This page updated:
Jesse Brett's "Drive System Maintenance and Repair"
summarized from article by Steve D'Antonio in Sept 1996 issue of Cruising World magazine:
- Nuts should be tight.
- Inner nut should butt directly against propeller.
- Small/shallow nut should be first (closest to prop).
- Check cotter pin.
- Looks for chips, dings, dents.
- If tips corroded, may be electrical corrosion.
- If whole surface is pink, prop has been dezinced (replace).
- If back surface pitted/rough, cavitation (probably pitch too large).
- Check clearance of each blade tip from some fixed
point (screwdriver clamped to strut).
- Check shaft deflection at several points
(ends, and two points between log and strut),
sanding surface first, using clamped screwdriver.
- Remove prop and inspect key and keyway: key should fit tightly,
must be absolutely no cracks in key or forward end of keyway.
- Threads should be good.
- Cutless bearing:
- Should not be more than "slight movement" when shaken
(especially when it's wet; more when dry).
- If "thunk", replacement is overdue.
- If brass and pink-colored and crumbly, electrical corrosion.
- Fiberglass-shell bearing is easiest to remove.
- Installing a new metal-shell bearing: put it in the freezer for
a day before installing, to make it shrink a little.
- "Movement of the slightest degree is unacceptable."
- Want silicon bronze, not stainless, bolts.
- Want a backing plate for the bolts.
- Stuffing box:
- Want special thick-wall (at least 5-ply) hose, not ordinary water hose.
- Want solid (not perforated) stainless steel hose clamps.
- Some stuffing box nuts are reverse-threaded.
- Stern tube:
- Make sure shaft is not chafing against inside of tube
(have to remove shaft, maybe stuffing box and cutless
bearing to inspect !).
- May have cotter pin, set-screws, nut, and/or key and keyway.
- If set-screws, must be seized with wire.
- If set-screws, thread-locking compound will help keep them from rusting in place.
- Bolts should be mild steel grade 5+, not stainless (weaker).
- Bolts should have lock-washers and thread-locking compound.
- Stuffing box.
Without grease: constant slow drip of water.
With grease: no water drip ?
With dripless packing (Teflon or graphite).
Gives wet bilge; may score the shaft.
- Shaft seal: bearings or O-rings, with natural water or forced-water or oil lubrication.
PYI's PSS Shaft Seal ($240 for 1-1/4" shaft)
Tides Marine (forced-water)
May be hard to inspect.
Forced-water usually tapped from engine raw water cooling hose,
adding another point for a catastrophic failure.
Dripless shaft seal review in 11/15/2000 issue of Practical Sailor.
- Lip seal.
Rota-Seal (press-fit rubber ring).
Tides Marine nitrile lip seal
PYI's PSS Shaft Seal
From Mike Z on Cruising World
I have had a stuffing box, shaft seal (bellows and clamp mechanism),
and lip seal (Tides Marine), each for several years with constant use.
There is no question that the lip seal is best.
Stuffing boxes need adjustment, damage the shaft, and, of course, drip.
... shaft seals can lead to disaster if there is even a minor failure,
and things do get loose / go bad on them.
[With a lip seal, keeping] an extra [spare] lip already on the shaft means it can be
inserted into the unit easily with the boat left in the water.
The lip can wear or even tear, but the result will likely be a drip no worse than a
badly adjusted stuffing box. Go with a lip. They are even cheap.
From Tides Marine 4/2004:
Our unit would replace the entire existing stuffing box. In the case of a
refit, shaft condition in the area where the lip seal itself would ride must
be good. This means that the shafting should be free of scratches,
toolmarks and scuffing from the old stuffing box. The lip seal in this
application would ride about 5.75" ahead of the end of the existing stern
tube. List price on the unit is $335, and if you have room the spare
seal carrier lists at $84. You would need to provide us with the OD of
the stern tube in addition to the shaft diameter.
All of our shaft seals must be [forced] water lubricated. The complete unit inclusive
of shaft seal, silicone mounting hoses and clamps is $335. The spare seal
carrier is a protective shell containing a single replacement lip seal. It
lists at $84. It is listed separately as some installs do not have room
available to fit it. If it is fitted you can change the lip seal without
hauling the boat, with common hand tools in about 15 minutes.
From Rota-Seal 4/2004:
Nitrile seal for 1.25" shaft about $11. Minimum order is $25.
You press the seal up against the flat surface, and rotation of the shaft
seats it in place. The seal is bi-directional and self-locating; it should not matter
which direction the shaft turns. The seal will need to run against a smooth
surface to extend seal life.
From Bob Taylor on the
WorldCruising mailing list
Have had a PSS Seal on my boat about 5 years now. Love it.
No water has entered the boat through
the shaft log since. Get the one with a carbon wear ring, not plastic.
I have heard the plastic ones will melt and leak if run dry.
From Gary on Cruising World
Installed a PSS shaft seal from PYI almost 6 years ago,
and have had flawless performance and a dry bilge since.
Word of caution - if you have a PSS, and you have your
boat hauled, you must release the air captured in the
shaft tube when your boat is relaunched. It is a simple
procedure. You simply pull back on the bellows tube when
the boat is in the water to release the air, and let the
water come all the way up the shaft. If you look at a
schematic, you'll understand this.
From Justin/PYI on Cruising World
... Pro's - dry bilge (or easier to identify your other leaks!)
No adjustment necessary. No accidental scoring of the shaft.
A seal like the PSS seal will work even if you have a small
amount of shaft vibration.
Gary is right about "burping" the seal before launch.
If that doesn't tickle your fancy you can get a high-speed
option with a hose barb threaded into the graphite flange on
the seal. Run a hose from the nipple to your seawater cooling
system or vent way above the waterline and you eliminate
the pocket of air normally trapped during relaunch. Voila!
No more burping. Adds about $25 to the cost of the seal.
As for installation, if you've got at least 5" between the front
of your stern tube and the back of your shaft coupling the
PSS seal will fit. ...
From Al Miegel on Cruising World
Have PSS from PYI, love it, no water at all in the bilge.
Only note to add is to expect a small amount of graphite dust
the first season until it "seats in". Inspect the
clamps annually as you would any below-waterline through-hull
and otherwise forget about drips, water in the bilge
and all the attendant ills it brings.
From Al Schober on Cruising World
The [high-speed version of the] seal will have a 'vent' fitting on top.
Hook this up to the output from your engine seawater
pump through a filter. This will keep the seal faces
running in nice clean water. A 50-micron filter should
do the job nicely. If the filter is any coarser than
that, don't bother.
From Howell Cooper on SailNet's Gulfstar mailing list
Regarding the PSS dripless, I have asked many professionals about it and
not one to date trust it. I know it is standard on many new boats and
many of our sailing friends swear by it. We also know of several who
have removed it due to chatter, no help from the makers, leaks and
downright failure. As one old-timer put it, at least the old packing
gland is predictable.
From Bob on SailNet's Gulfstar mailing list
I guess as in all things, some swear by them, others swear at them. I myself
have had the PSS for five years ... no problems. As a rigger, I recommend
them, as do several yards in the area. I guess problems can always
occur with any product.
From John Viera on "Tyche":
I installed the PSS Shaft-Seal, which is one of the best designs on the market according to
Practical Sailor. I like it because there is no maintenance required, but you do need to protect
it from oil getting onto the rubber seals, as this will cause then to deteriorate.
Tom Neale says stuffing can be replaced/renewed without hauling;
other types can't be.
SailNet - Tom Wood's "The Stuffing Box And Stern Tube"
Small "Dope for Stuffing" article in issue 2000 #3 of DIY Boat Owner magazine.
Article by Bill Sandifer in March/April 2002 issue of Good Old Boat magazine
Propeller/shaft/stuffing inspection article by Steve D'Antonio in Sept 1996 issue of Cruising World magazine
Replacing cutless bearing with a waterproof bearing:
Seems to me that the main problem is the cutless bearing, and its need to
have water run through it for lubrication. But no one seems
to replace that with a greased bearing. Why not ?
[Actually, I'm told
there just has to be water present
in the cutless bearing, not
it. The drip is needed to keep the stuffing
from heating and/or scoring the shaft.]
Large ships are going the other direction: replacing an oiled
bearing with a water-lubricated one, partly to reduce pollution
caused by escaping oil.
's EMSS has an
oiled bearing through the stern tube, but they require buying a complete
system which also replaces shaft and absorbs prop thrust in a "thrust bearing"
at the end of the keel
instead of on the engine mounts. About $4800 for my Gulfstar 44
(1.25" diameter shaft, about 4 feet from gearbox to stern tube)
plus $100 each for motor mounts.
From Evolution Marine:
... The shaft system
includes the engine adapter, internal connecting shaft utilizing
universal joints at each end and with splined slip joint to further
allow the engine to 'free float' on truly soft motor mounts rated just
for the engine's static, vertical weight. Also included is the 'oil
lubricated' section which is a alloy 22 s.s. shaft 1.25 inches in
diameter enclosed in a 316L s.s. shaft log tube. Inside of the vessel
this tube and shaft mate up to a larger steel diameter housing tapered
thrusts bearings for forward and reverse. Outside of the vessel the
same shaft and tube mate up to a bronze bearing assembly that contains
needle bearings, seals and races. Within the shaft log tube there's
Once the system is installed, the prop thrust will have been transferred
to the hull ... the cutless bearings and packing glands will have been
Vibration from the engine to the hull is reduced significantly. Also,
vibration from the prop to the hull is also reduced significantly. With
less vibration, we have seen noise levels reduced by 17 decibels. Also
with less prop vibration, we have seen increases in speed and fuel
utilization since typical propeller slippage is reduced. This is
accomplished by the extremely close clearances between mechanical
bearings as compared to rubber cutless bearings. ...
> I'm curious about the "prop thrust will
> have been transferred to the hull" angle of it.
> I'm sure the hull designers put in strong
> engine beds, expecting the thrust to be on them.
> With EMSS, the thrust will be on the shaft tube
> area of the keel, right ? Any concerns about
> that area not being strong enough ?
Since both assemblies (thrust bearing and aft bearing) are attached to
the s.s. shaft log tube plus the shaft is captured within the thrust
bearing assembly ... the oil lubricated section is ONE PIECE. Where one
would grap it initially is where the thrust is ... even though the prop
thrust dead heads inside the vessel at the thrust bearing assembly.
For example: We tell people with a strut configuration that the
internal bulkhead to which the thrust bearing assembly is bolted
to ... must be strong enough to accept 100% of the propeller thrust for
forward and reverse gears. If the vessel has a full keel or sternpost
with an existing two or four bolt external cutless bearing assembly, we
can produce a duplicate flange to which our aft bronze bearing assembly
mates up to. If this is the arrangement, then the prop thrust is
captured outside right at this flange. If the sternpost were to be weak
and wiggle, one would see the corresponding movement inside at the
internal bulkhead. However, this simply doesn't happen since this tends
to be the strongest point of the hull.
Another arrangement for installation of the EMSS is to allow us to
attach a fiberglass stern tube (typically used for cutless bearings,
etc). We machine the aft face, drill and tap for six 3/8 s.s. bolts.
The circular bronze flange has a pilot that goes into the fiberglass
tube. Before bolting together, we seal with marine sealant. The
boatbuilder or boatyard takes the unit into the vessel and slides the
entire 'oil lubricated' section from inside the vessel outward. Outside
the vessel, the yard then fiberglasses the hull to the fiberglass stern
tube and they are done outside. Inside of the vessel they lay the
forward part of the s.s. shaft log tube into a U-shaped bulkhead to
maintain the shaft angle desired.
> And I guess you've answered my other question:
> since the oil-lubricated section is one piece
> all the way to the thrust bearing, I can't
> buy just the stern-tube bearing from you,
> right ? I'd really like to replace just
> the stuffing box and cutless bearing, with
> an oil-lubricated bearing through the stern
> tube, and leave everything else unchanged
> (old shaft, thrust onto engine mounts, etc).
> But you don't sell just an oil-lubed bearing
> for the stern tube, do you ?
... we manufacture and sell the complete system.
At one point, we wanted to be the "Sears Roebuck" of shaft
components ... in that, we wanted to have price alternatives to our 'Rolls
Royce' EMSS ... so we developed a unit comparable to Aqua-Drive. By the
time we priced it out with expected margins, we were selling it at 60%
of our complete EMSS. For the additional 40%, and the very significant
benefits ... we stopped building the abbreviated version. ...
Replacing stuffing in stuffing box, from Rick Kennerly on
Yacht-L mailing list
... get one of those little flax picks (has a
really wicked looking corkscrew on the end of a flexible wire). It
will make getting that last piece out much easier.
I've used the teflon grease and the harder flax that goes with it on
our Westsail 32 with a 50 hp Perkins 4-108 in it. It's a bit slimy and
messy, but works great. This is our 3rd season with it. The only
drawback to the teflon grease is that makes the flax so slippery that
you can't put two or three rings on the shaft and slide them in
together (like you can with grease because the grease makes them stick
to the shaft).
If you try to do this in the water, figure what you're going to do if
you can't get it back right. 8 pm on a Friday evening is not the time
to be looking for a travellift operator. Once you've done it a couple
of times you get the hang of it, but it is a bit nerve wracking the
first time in the water.
Before you open the gland up, prepare everything first. Cut your flax
this way: Wrap the flax around the shaft in a spiral. Take a sharp
knife (a razor knife works well) and cut through two of the rings at a
45 degree angle This will give you one complete ring that has
overlapping ends. Don't try to cut 90 degree angles as butt joints
will leak. Cut as many rings as you need and when you pull the gland
back arrange them on the shaft with the cuts staggered at different
"o'clocks" around the shaft. Use the packing nut to run them into the
gland evenly, each new flax piece pushing the ones ahead of it into
Don't forget the locking nut when you're finished. Too loose is better
than too tight. Remember that a slight drip when running cools the
shaft and prevents scoring of the shaft. Watch it for a day or two
until it settles down. I've had new flax that wouldn't seal at all
for the first day no matter how many lines I put in or how tight I
cranked down on the packing gland nut and some that would never leak,
even with the packing nut almost off and the prop turning over.
"The Zen of stuffing boxes",
from Roy Miles on Cruising World
A conventional stuffing box acts exactly like the faucet valve on your sink.
It has to turn in an environment where water under pressure wants to
leak along the shaft. The packing nut on both a stuffing box and a
valve stem cranks down on a base, squishing the packing material inside
against the shaft. When either begin to drip excessively, you tighten
down some more. Eventually, you need to change the packing because
it's all "squished" tight.
Stuffing box packing is pretty robust stuff, made of waxed teflon
or flax, generally woven in a square section. You buy it at marine
stores in packages sufficient to seal one stuffing box.
When you arrive at the point where tightening no longer works to
stop the drip, it's time to change the packing. It's not rocket science,
it doesn't cost much, and you can do the job without hauling the boat.
You will need a minimum of tools: good lighting, a pair of large wrenches,
some needle-nose pliers (preferably right-angle), a piece of stiff wire,
a razor knife, and a measuring device (tape, ruler, or calipers).
You will be working on your knees, possibly in an uncomfortable
position, so make the necessary accommodations.
Expose the stuffing box, and get your tools arranged nearby.
The packing nut is directly held tight by a locking nut,
located aft of the packing nut. If the stuffing box is dirty,
it may appear to be one big nut. Place a large wrench on each,
and loosen the lock nut from the packing nut, then back the lock
nut off as far as you can (thereby cleaning the threads on the base).
Next, back the packing nut towards the engine, away from the locking nut.
WHOA!!! Look at all that water rushing into the bilge!
Don't worry, you have a bilge pump, and it takes a lot of water
to sink the boat. Slide the packing nut back along the prop shaft
so that you can look at its interior. You will see a space between
the shaft and the threaded portion of the packing nut. Measure this,
if you can. If you can't, estimate it. Then tighten the packing nut
back on the base until the flood tapers down to a less terrifying stream.
Go to the store and purchase a package of packing of the size you
measured (or buy the most reasonable sizes
according to your estimate). You can even do this ahead of time
by telling the salesperson your prop shaft diameter and (if you
know it) stuffing box manufacturer.
You're back now, on your knees, admiring the stream of water
entering the boat. Wrap the length of packing material around the
prop shaft. You will probably have at least three full wraps,
plus some extra. Keeping the wrap as tight as possible, run the
razor knife along the length of the shaft, cutting all the strands.
Remove the pieces, keeping the three best ones nearby. Once more,
remove the packing nut, admire the pressure of the cold seawater
flowing in, and begin to remove the old packing from the inside
of the packing nut.
This is the most difficult part now, but it gets much easier in
a couple of minutes. Using wire, needle-nose pliers, or, if you have
access to one, a cork-screw looking tool mounted on a spring with
a tee-handle [or a cheap dental pick, or a large fish-hook straightened out],
remove the pieces of old, squished packing.
Get it all out, then scrape around inside the packing nut to confirm
everything is clean inside. Place the three new rings of packing
around the shaft between the base and the packing nut.
Gently ease each ring into the packing nut space between the shaft
and the thread. Be sure that the cut section of the packing material
is staggered with respect to its adjoining piece (much like piston
rings in an engine. When it's all inside the packing nut,
gently slide the packing nut onto the threads of the base and
begin to screw down until the leak stops.
Stuffing boxes are dynamic, meaning that they require regular adjustment.
This means that the thing is going to start leaking as soon as the
shaft begins to turn. It's supposed to, thereby keeping the shaft
lubricated with seawater and cool when turning. So, the dynamic is this:
Stop tightening JUST as the drip stops. Don't crank down as hard as
you can. Fire up the engine, make sure the spring lines to the dock
are secured, and put the boat in forward gear, slowly. Water will
begin to drip through the packing nut. Gently tighten the packing nut
until the drip rate is about one drip per second. Increase the RPM to
cruising speed, and if necessary, tighten again to the one-drip rate.
Now, shut the engine down and watch the shaft. If you have adjusted it
sufficiently, the friction of the shaft against the packing material
will now be cooled by the leaking seawater to the point where the
wax congeals, STOPPING THE DRIPS! It's a dynamic because you sometimes
need to play with the tightening a few times to get to this
point. Voila! The shaft drips underway and seals when it stops ...
until, one day, you notice that the drips don't stop at the end of use.
That just means that you need to tighten down the packing nut once again,
gently, as before. Oh, lest you forget, after you get the adjustment
correct, then tighten the lock nut against the packing nut to keep
that level of tension.
Stuffing boxes are simple to use and to maintain.
Lots of folks get intimidated by them and switch to more expensive
packing-free stuffing boxes. Or, sometimes, naughty builders install
them in places that normal humans can't work on them.
There is a special place in Hell for these builders.
Then you might consider the other form of stuffing box.
Keep a spare length of packing in the tool box for an eventual change,
but it shouldn't be necessary for several years.
From Larry Dill on the Morgan mailing list
Stuffing Box Packing:
I replaced my shaft and bearing last spring. I used the stuff West has that
has PTFE in it. I applied the PTFE lube they sell along with the packing.
I also gave everything a final soaking before closing it up with the Super
Lube from K-Mart (Silver spray can -- has PTFE in it as well). I have the
gland running only hand tight, and no dripping. I figured that it would
commence dripping once it was broken in a bit. I motored for approximately
600 miles with this set up last summer -- no dripping (I frequently wrapped
my hand around gland and shaft after shutting down to see if it had
warmed -- found nothing unusual). Recently, I backed off the packing nut,
expecting that maybe I had scored my new shaft. It was as smooth as new.
I do have a few more layers of packing than one might normally put in. As a
result, the nut is not as far onto the gland as one would normally expect (I
left it rather loose, and ensured that the lock nut was snug). My theory
is that if you use extra packing (there is a limit to how much you can
reasonably use), then limit the compression, the packing will be placing
very little pressure on the shaft, thus minimizing scoring. I would add
that several times I tried to get my packing to drip, but to do so, I'd have
had to remove packing or back the nut out until it was hanging by only a few
threads. I was lucky -- had I found scoring, I'd have been pretty unhappy
with myself for not going ahead and pulling out some of the packing to make
the thing leak.
I am not suggesting that you try this, but it worked for me.
From Bob Clinkenbeard on The Live-Aboard List, 7/2001:
With new flax packing in place ... the proper way to tighten the packing
gland nut is to slowly tighten the nut when the boat is in the water and at
rest, until the drip ceases. When you run the boat, shaft is turning,
there should be a drip every few seconds to keep the shaft cool and the
packing from burning. When you stop ... the drip should also stop.
The shaft/stuffing box should not be so hot that you can't hold your hand on
it. Warm is from friction and ok. Hot is going to score. You should be
able to turn your shaft by hand when it is disengaged.
Old packing will not adjust this way. It will be hard and dry and will
probably leak all of the time no matter what you do. If you tighten old
packing too tight it will burn the shaft = score the shaft.
There are many types of packing ... some claim dripless, teflon, and greased,
Packing should be replaced when you can't adjust it as I have described
above ... it has become hard and dry.
From 4/15/2004 issue of Practical Sailor:
Stuffing box hose: don't use hose with embedded wire in it; that may rust over time.
Use hose with fiber reinforcing. Typical hose is wet exhaust marine hose.
Large supplier: Buck Algonquin
From Um Saudade on World-Cruising mailing list:
Re: dealing with a worn spot on the shaft:
In most boats the stuffing box is connected to the shaft tube by a piece of flexible hose.
In most cases this hose does not have an absolute predetermined length. If you can cut some of the hose
off (or reconfigure with a longer hose) you will be able to relocate the packing on a fresh part of the shaft.
In many cases a quarter of an inch is sufficient to get away from the wear point. If installing a new shaft,
start with a long length of hose, making it possible to shorten the length at a later date if the shaft shows excessive wear.
Designed to break if overloaded,
electrically isolates propeller from engine.
Globe Rubber Works
From Dave Boatman on Live Aboard Mailing List:
I have been using a Drivesaver for seven years for
all three of the listed reasons [vibration/tranny
protection, isolation/corrosion, ?]. It already saved
my drivetrain once when a yardworker threw a line
into my prop while I was backing out of the
slipways (go figger!). It 'exploded'
and I simply bolted the coupling back together.
Drove to my slip and ordered a new one
immediately ... zero damage.
It has offset boltholes to provide galvanic
isolation of the prop and shaft
and assists in adapting the shaft alignment
to tiny imperfections in alignment and vibration.
I love it and keep a spare in case I run over
a fishing net or object in the water.
From Patrick Matthiesen of Sparkman & Stephens Association
in Good Old Boat
... remarked on the problems he had securing a Drivesaver to his coupling.
If he is using a genuine Drivesaver (red in color), he should not encounter these
problems, but his problems should be alleviated if he fits cut or spring lock
washers under the nuts securing the disk to his engine and gearbox flange.
If he wants to be doubly sure, he should drill
the ends of the bolts and use castellated nuts and secure them with a wire or pin.
However with spring washers, this
should not be necessary. If the disk is working loose from the flange attaching
the tail shaft, he should try spring washers
as indeed is recommended by the manufacturer. This would be an unusual failure.
Over-tightening of these bolts tapped
into the plastic disk may well strip the threaded holes in the disk.
I would venture that he should first check his shaft and see that it runs true.
If it does not, he could take a close look at
his prop to see if a blade is damaged, worn, or pitted (an unbalanced prop will
wreak havoc) before fussing with the
niceties of engine alignment. One thing is for sure: if he has an alignment
or prop problem, no amount of Loctite will hold the assembly together!
From Lee Haefele on The Live-Aboard List:
> I'm considering a flexible coupling (i.e. R&D Marine) ...
I have an original equipment flex coupler. It has been a source of confusion
as to getting the shaft aligned, I can only get the alignment to .008", and
that rotates with the shaft. I also had issue with not engine alignment but
with the coupler/transmission connection being offset .020-.050". The #$%@
thing adds about 2-4 hours to shaft removal and again on installation (more
or less depending on access). Then I wanted to buy new rubber bushings, but
could not identify the coupler. If I bought new bushings from Vetus, they
were over $200/set. ... My coupler has
a ground strap [to preserve conductivity for grounding].
My ownership of a flex coupler has not been a positive
Transmission-to-shaft CV joint:
From Lew Hodgett on the IRBS live-aboard mailing list:
... CV joint such as an AquaDrive: you bet your
sweet fanny they are worth EVERY penny you pay for one.
Added one to a Yanmar YSM-12 (a one-lung beast) that kept breaking engine
mounting studs on a regular basis.
Sound level reduced about 30 dB.
Quit backing fasteners out of bulkheads, etc.
Never broke another mounting stud.
Will definitely put one on the boat I'm building. Won't leave home
From Mike Laaper on Cruising World
I had a 1979 Vancouver 27 with 16 hp Kubota, worked fine. Now have a
Young Sun 35 with Yanmar 30 hp, the noise used to drive me crazy.
In 1990 in Mallorca I installed an Aqua drive, has worked great and
have been able to live with the greatly reduced noise levels, never
bothered to put in more sound insulation, which was minimal to start with.
The Aquadrive comes with a thrust bearing which will have to be mounted on
a small bulkhead to take the thrust, now the thrust won't be taken by the
engine mounts any more so you can install a lot softer mounts, aquadrive
will advise as to what hardness of mounts to use. It all sure worked for me.
still happy with it after 13 years.
From Charlie Stillman on Cruising World
My system was designed from the get-go to use an aquadrive, so everything from
engine beds on up was meant to live together. Certainly poor shaft alignment
in addition to prop issues mentioned by mobetah could contribute to vibration.
Maybe the engine mount rubber needs replacement.
Have you observed the engine running in neutral, then again running in gear?
If the engine "hobby-horses" in gear, that would be caused by poor shaft
alignment which can be corrected. The outfit you are talking with may
have already checked shaft alignment.
A few things about the aquadrive units. They require a solid mount at the
aquadrive's aft end for the thrust bearing part of things. Shaft alignment
is not that critical for the aquadrive, but the drive train must be set
up with a couple degrees bend. Otherwise, it will not get lubricated properly.
An aquadrive allows you to float the engine on softer beds, lessening vibration.
The units are basically automotive CV joints in design, and like many things
mechanical, they do wear out. They need to be rebuilt at something 1000-2000
hours if my memory serves. If your supply chain is long, you may want to keep
a some spare aquadrive parts on board.
Take my advice as one data point. Find yourself a good marine engine person you can trust.
BTW ... I'm very satisfied with our aquadrive. The 4JH turbo Yanmar and
aquadrive make a silky smooth combination.
about $1400 for 110 HP.
Requires strong cross-member aft of gearbox, to
attach thrust mounting to.
Doesn't replace cutless bearing or stuffing box.
From K. Chin on The Live-Aboard List:
Regarding getting your prop shaft off the coupling:
A mechanic I knew offered me this tip. It's really
simple and you don't need lots of fancy tools.
1) Before you completely separate the shaft
coupling plate and the engine coupling plate, loosen
all the bolts that hold them together just enough so
that you can slip a nut between them. This nut should
be placed snugly right at the center of the end of the
shaft that is between the coupling plates. You may
have to use tape to hold it at first.
2) Now go back and tighten all the perimeter bolts --
slowly and evenly all around. This will compress the
nut that you just placed at the end of the shaft
(between the plates) and it will force the shaft out
of the coupling plate in the opposite direction.
3) Lots of penetrating oil (WD-40 etc) on the
shaft-coupling will also help.
4) As the shaft slowly gets pushed out, you may have
to stack more nuts together (with tape etc) to
increase the spacing.
5) Continue this process of increasing the nut spacing
and compressing the nut until the shaft is eventually
From Gene T on Cruising World message board:
On having trouble removing a propeller shaft:
I would check the way the boat is blocked up. Some boats have enough flex in the hull to cause
distortion between the shaft log and strut if the jacks are improperly placed. Of course the shaft
could be bent.
From W G Nokes on SailNet's Gulfstar mailing list:
Re: shaft lock
I stick a cheap screwdriver in the coupler bolts and against the hull. If
I forget to remove it prior to putting engine in gear, the screwdriver
shaft merely bends and it falls into the bilge. Most times there is a small
counter movement to the shaft before it spins, and the screwdriver merely
drops into the bilge.
From Rick on SailNet forums:
A simple brake can be made from two pieces of 2x4 with a a V cut into each and clamped
together with carriage bolts with springs and wing nuts.
Just tighten the brake enough to stop the shaft.
If you start the engine it will allow the shaft to spin, but if you run for too
long the wood will start to overheat and let you know you forgot it.
From bobola on Cruising World message board:
Re: replacing cutless bearing:
From Paco PWD on Cruising World message board:
Found this online:
For removal of the old bearing:
1. Use ready-rod or pipe clamps (the clamps that use a 1" steel pipe to form
the backbone of the clamp) to exert pressure in a controlled manner in alignment.
Combinations of sockets or large washers or short pieces of pipe need to be used
to make contact with the bearing and strut. If you cut off a piece of pipe to suit,
and it is not absolutely dead true, the pressure may be at an angle and cause the
bearing, socket etc to dig in. Try not to hammer the bearing and strut. Check that
the strut is not loose where attached to the hull.
2. If the old bearing will not press out, relieve the tightness by threading a hacksaw
blade through the old bearing (teeth forward and down), and hook up the hacksaw
underneath it, upside down. You should now be able to carefully cut downwards through
the rubber and into the brass/bronze shell of the bearing. Be VERY careful not to cut
into the strut itself at either end or damage it in any way or it could start a fracture
from that point when under stress.
3. Use sandpaper or emery cloth to remove any irregularities inside the strut.
It is particularly important that no burrs etc be at the point where the new bearing will enter.
For installing the new bearing:
4. Be very careful in aligning the bushing for installation and ensure that pressure on
the end of the bearing does not distort it.
5. Remove any sharp edge around the leading end of the bronze sleeve around the rubber
bushing before you press it into place so there is no chance of it binding on entry.
It is very tight (usually called an interference fit or friction fit in the trade).
Make sure that you lubricate it with something like grease.
6. The new bearing may seem a bit loose, but apparently will "crush" in a bit upon installation,
making it smaller and tighter on the shaft.
7. You do not need a lubricant between the shaft and rubber bearing; the water will do that.
From Jim T:
You need a sleeve or socket that has just under 1 1/4" OD to press out the cutless bearing,
and another with a 1 1/2" ID. I purchased about an 18" length of 1/2" threaded rod stock
from Home Depot with nuts and some large washers. To press out the cutless bearing you use
the rod to draw the under 1 1/4" OD socket/sleeve against the cutless bearing, pressing
the cutless bearing out through the strut into or through 1 1/2" OD socket/sleeve which
is bearing on the aft surface of the strut. You can also thread a hacksaw blade through
the cutless bearing and carefully cut through it without cutting into the strut.
Pressing the new one in is easier (not easy, easier) ... just use the rod and washers.
Be careful to keep it centered and aligned to prevent crushing it. Do not use petroleum
products to lube the cutless bearing; they can damage the rubber bushing.
Installing new one: get it a bit longer (not much) than the strut; that will allow you to get it moving easier next time.
And freeze it just prior to install. Worked for me twice !
From Captain Robbie_D on Cruising World message board:
(I have seen a guy who lubed his bearing; the rubber bushing swelled
to a point where the engine could not turn the shaft.)
I replaced about 20. If there is play, replace it. Order one from Fawcetts in Annapolis for $50.
Vibration is the WORST thing for your hull, packing gland transmission and engine mounts.
OK. The setscrews that hold the cutless bearing in whatever it is in are often Allen heads
and there will (always in my experience) be one on either side about midway down the length
of the bearing housing. Scrape the paint off and FIND them. Dig the holes out BEFORE you
try to remove them. If you strip them you have to drill them out and tap a new hole.
They are HARD to find if there are a lot of coats of bottom paint.
If you are lucky they are bolts with holes for mousing wire. Anyway, get them out.
Most times you do NOT need to pull the shaft out, which is good because couplers rust
and it can be a bear to get the shaft out after you take its setscrew out.
Take the prop off and once the bearing setscrews are out usually the bearing will slide out and off.
Tapping lightly with a brass punch will almost always do it, and a little spray lube/solvent (WD 40) may help.
If the cutless bearing housing is in the hull, you probably will need to pull the shaft,
but you may be able to pull it out by drilling a small hole you can thread a screw in in
the old bearing and pulling it.
Put the setscrew back with loctite, unless they are mousable bolts then make sure you rewire them with monel.
My experience 5/2006:
- Couldn't get prop off the shaft without attaching a huge puller,
heating the prop with a propane torch, and hammering on the prop. Had to
repeat several times over several hours before the prop suddenly sprang off.
[This was surprising, since I'd had the prop off the shaft 3.5 years earlier
with little problem, and had put a lot of marine grease on to make it easy to get
off again. Maybe the grease was the wrong thing to do ?]
- Couldn't get the aft half of the transmission coupler off the shaft.
Got the setscrews and key out, although one of the setscrews required use of a torch to free it up.
Tried the trick of putting a socket between the coupler halves and tightening the halves together, but didn't work
(maybe because I have a DriveSaver); it was very hard to see if the socket was in the
Attached a huge puller, heated the coupling half with a propane torch, and hammered on the coupling half.
Then bolted the coupling back together, put the prop on, and hammered end of shaft and prop to try to
move the shaft within the coupler. Then the yard used a slide-hammer on the end of the shaft,
and that worked. Last resort would have been to use a grinder
to cut the coupler half open, and install a new coupler half.
- Cutless bearing setscrews came out easily, but the bearing was well frozen inside
the stern tube. Since the tube was much longer than the bearing,
it wasn't possible to tap on the forward end of the bearing from inside the boat.
Had to get the yard to cut it out with a SawzAll.
- The mechanic said the old cutless bearing was in terrible
shape (I didn't get a close look at it, and didn't get it back later).
I guess 10 years, including a trip down the silty Mississippi River, was
too long to go between changes.
- Spare cutless bearing I had on board turned out to be the wrong size !
And stern tube seemed to be bigger diameter at aft end than at forward end,
although it's hard to tell.
- Put new cutless bearing in freezer for a day to shrink it, before installing.
- Leave 3/4" to 1" of aft end of cutless bearing protruding past aft end of stern tube,
to make it possible to grip it with a pipe wrench the next time you need to replace it.
That might let you replace it without pulling the shaft.
- Carefully drill slight dimples in cutless bearing through the
setscrew holes, to give the setscrews something to bite ? My bearing was
such a snug fit that I doubt this is necessary. And holes for 2 of 4 setscrews
were stripped anyway.
From Gypsy DJF on Latitudes and Attitudes Cruisers Forum:
Best price found for propeller shaft was at Marine Hardware Inc in
Seattle; best price for cutless bearing was at Pyacht.com
General Propeller (props, shafts, couplings)
Buck Algonquin (stuffing boxes, shaft struts)
A source of Gore-Tex GFO packing: Phoenix Packing & Gasket Co, NJ, 732-938-7377.
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