I have a Scampi 30 sailboat. The shaft has a thrust bearing behing the
propeller that is made out of some kinda oil impregnated plastic. This
is wide open to the outside. I want to replace this friction bearing
with a thrust roller bearing. I am thinking that I should get an
encapsulated stainless bearing but I cant find such an animal. Can
somebody point me in the right direction, or tell me if this is a good
idea.. Thank You

To me, this is a bit confusing??

Does your boat have an inboard engine with a propellor shaft?? or are you
talking about an Outboard motor or Out drive??

A properly installed marine engine will have the thrust bearing in the
reduction/reverse gear. If it is an OB or Out Drive, the thrust bearing is
inside the lower unit. I've never heard of a thrust bearing at the
propellor. There should only be a water lubricated cutlass bearing.

Please provide more information on what you have, engine/rev. gear, etc. and
maybe we can figure a solution.

Steve
s/v Good Intentions

"Steve" wrote in message ...
To me, this is a bit confusing??

Does your boat have an inboard engine with a propellor shaft?? or are you
talking about an Outboard motor or Out drive??

A properly installed marine engine will have the thrust bearing in the
reduction/reverse gear. If it is an OB or Out Drive, the thrust bearing is
inside the lower unit. I've never heard of a thrust bearing at the
propellor. There should only be a water lubricated cutlass bearing.

Please provide more information on what you have, engine/rev. gear, etc. and
maybe we can figure a solution.

Steve
s/v Good Intentions

Here is a link that shows a diagram of the boat
http://home.worldonline.dk/sejler/scampi/scampi.htm
This boat has an hydraulic drive system. The brace that you see in
front of the impeller is where the bearing should be ( I think) It
looks like a very strong support made out of metal and imbedded in the
fiberglass.

john m says:

This boat has an hydraulic drive system.

Probably just a hydraulic gearbox, from the looks of things...

The brace that you see in
front of the impeller is where the bearing should be ( I think) It
looks like a very strong support made out of metal and imbedded in the
fiberglass.

THat would be called the strut, and the bearing in it is just a cutlass
bearing, Rubber in a metal tube. It is supposed to be like that, as it's only
job is to support the shaft. The actual thrust bearing is inside the boat,
usually either just aft of the transmission, or integral to the tranny.

Steve

From what I see of your drawing, the fitting your discribe forward of the
prop is a standard strut.. I doubt that your strut installation is made to
take the full thrust of the propellor..

I agree with Matt.
Conventions would have the thrust bearing in the hydrolic pump and only a
cutlass bearing in the strut.

I suspect someone has tried to 'Improve' the installation.. Or the hydraulic
motor has a bad thrust bearing.

If in doubt, contact the manufacture of the hydraulic motor and determine if
the the motor has a thrust bearing in it.. If so then you need to verify
that it is in good condition and leave the one you found out of the
installation..

Or there is another possibility, that the original builders hydraulic motor
went bad and some one put a conventional/industrial replacement in it's
place. In this instance the industrial motor most likely wouldn't have a
thrust bearing.

Just my speculation, FWIW.

Steve
s/v Good Intentions

John,

Yes, I was contracted to repair the strut bedding when the boat got run
with a damaged blade. That boat did not have the couple you describe
between the hydralic motor and the prop shaft. There was also no
conventional stuffing box. The prop shaft is enclosed in the stern tube
from the after end of the strut into the hydralic motor. The motor is
actually attached tot he stern tube and is supported by both that and a
torque brace.

After we got all of the other stuff fixed, the boat still would not make
more than 4 knots and the engine was not loading. It back like a mad
man. So the owner got another set of blades for the other rotation and
shifted the pump to astern for ahead and now makes hull speed just fine.
When I talked to him last he was trying to find someone that knew how
to overhaul the pump and motor. When I see him next, I will ask him.

A chain coupling in a drive shaft is rare and not a proper application.
There is no way to put an axial load bearing (thrust) inside the stern
tube, so it must be in the hydraulic motor. That is part of why the
plastic washer is both installed and torn up. I suspect the washer is
required to keep the coupling halves from wearing on each other.

It is, however, not costing you horsepower. Bearings going bad can
cause vibration and failures, but if they eat horsepower they burn up
real fast. I suspect that if you are short on boat speed as you seem to
say farther down the thread, you have hydraulic drive problems just like
the Scampi I know had (may still).

I would see about getting both the pump and motor looked at before you
invest much effort in other paths.

Good Luck

Matt Colie - See Prior Sig

john m. wrote:

"Steve" wrote in message ...

To me, this is a bit confusing??

Does your boat have an inboard engine with a propellor shaft?? or are you
talking about an Outboard motor or Out drive??

A properly installed marine engine will have the thrust bearing in the
reduction/reverse gear. If it is an OB or Out Drive, the thrust bearing is
inside the lower unit. I've never heard of a thrust bearing at the
propellor. There should only be a water lubricated cutlass bearing.

Please provide more information on what you have, engine/rev. gear, etc. and
maybe we can figure a solution.

Steve
s/v Good Intentions


Here is a link that shows a diagram of the boat
http://home.worldonline.dk/sejler/scampi/scampi.htm
This boat has an hydraulic drive system. The brace that you see in
front of the impeller is where the bearing should be ( I think) It
looks like a very strong support made out of metal and imbedded in the
fiberglass.

Why do you want to replace it?

Brian W

On 8 Mar 2004 18:22:01 -0800, (john m.) wrote:

I have a Scampi 30 sailboat. The shaft has a thrust bearing behing the
propeller that is made out of some kinda oil impregnated plastic. This
is wide open to the outside. I want to replace this friction bearing
with a thrust roller bearing. I am thinking that I should get an
encapsulated stainless bearing but I cant find such an animal. Can
somebody point me in the right direction, or tell me if this is a good
idea.. Thank You

Brian Whatcott wrote in message . ..
Why do you want to replace it?

Brian W

Less friction. I want all the energy of the 12hp diesel engine to go to the prop.

On 9 Mar 2004 16:16:15 -0800, (john m.) wrote:

Brian Whatcott wrote in message . ..
Why do you want to replace it?

Brian W

Less friction. I want all the energy of the 12hp diesel engine to go to the prop.


Hmmm...if it's really, really sticky, it might be using 0.5 even 1 HP

If it did though, it would wear out in about 20 - 50 hours.
But it hasn't. And if it was that sticky, you STILL couldn't tell
the difference if it was replaced with a fabulous Zero-Friction
bearing made of Unobtainium (in my humble view).
So the best advice I could offer (which because it is free, I don't
suppose you will take up) is...leave it alone until it is a REAL
problem.

Good luck

Brian

John,
The only Scampi I have ever been real close to had a Farrimann diesel
hoooked to a Standadyne (I think) hydraulic drive. The actual thrust
bearing on that is inside the hydraulic motor.

The prop shaft bearing had worn and the owner got another bearing
somewhere and since he could not upull the original out without
completely disassembling the drive motor, he just pushed it in with the
new bearing.

Matt Colie

john m. wrote:

I have a Scampi 30 sailboat. The shaft has a thrust bearing behing the
propeller that is made out of some kinda oil impregnated plastic. This
is wide open to the outside. I want to replace this friction bearing
with a thrust roller bearing. I am thinking that I should get an
encapsulated stainless bearing but I cant find such an animal. Can
somebody point me in the right direction, or tell me if this is a good
idea.. Thank You