Bow Thruster maintenance fail


Kevin Schmit
 

Afternoon,

looking for some wisdom/advice….

I just completed my first bow thruster maint.  


While reassembling bow thruster with new lip seals I ran into an issue with the small seal that goes over the prop shaft.  While using a pipe to evenly push the seal over the last hump on the shaft the seal kept bulging out once full seated.   I would then take the unit apart and noticed the inside spring was no longer riding in the grove.  This kept after about 6 attempts.

I finally got the unit to seat properly only to find a puddle of hydraulic oil had leaked out over nite of the bow thruster.

I will order several more of the small size lip seals.

Any secrets to getting that seal to go on ?

thanks ahead of time.
--
Kevin & Kristen Schmit
KIANA
SM #362


 

Question: You wrote, "...a puddle of hydraulic oil had leaked out..."

It should be 90 wt gear oil.

image.png
image.png


Bill

CW Bill Rouse Amel Owners Yacht School
720 Winnie, Galveston Island, Texas 77550 
   

On Mon, Jun 13, 2022 at 4:46 PM Kevin Schmit <kevschmit64@...> wrote:

Afternoon,

looking for some wisdom/advice….

I just completed my first bow thruster maint.  


While reassembling bow thruster with new lip seals I ran into an issue with the small seal that goes over the prop shaft.  While using a pipe to evenly push the seal over the last hump on the shaft the seal kept bulging out once full seated.   I would then take the unit apart and noticed the inside spring was no longer riding in the grove.  This kept after about 6 attempts.

I finally got the unit to seat properly only to find a puddle of hydraulic oil had leaked out over nite of the bow thruster.

I will order several more of the small size lip seals.

Any secrets to getting that seal to go on ?

thanks ahead of time.
--
Kevin & Kristen Schmit
KIANA
SM #362


Bill Kinney
 

Kevin,

An additional hint that goes for ALL lip seals not just these.  Install them into the outer flange FIRST then gently push the shaft through.  Trying to keep them straight while working around the shaft is very difficult.  Without the shaft there, it is very easy to press them on straight.  Just a block of wood pushed down evenly with a clamp or two makes easy work of it.

If a lipseal has been installed and pulled out again, even once, the chances of it suffering irreparable harm are very high.  Although they last a long time once installed, they are rather fragile creatures during the install process.

Bill Kinney
SM160, Harmonie
Le Marin, Martinique


Roman Lawrence
 

Hello, to solve this problem, I took no hydraulik oil, but lsemifluid grease. That works perfekt....and nothing will run into the water.

see:
https://www.amazon.de/s?k=flie%C3%9Ffett&i=automotive&__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=4BW3KB5RZMRT&sprefix=flie%C3%9Ffett%2Cautomotive%2C77&ref=nb_sb_noss_2


karkauai
 

Guess I must be reading this wrong.  How would you place the shaft thru the lip seal already seated? Isn't there a 90° gear on the end of the shaft?

Have you confirmed that the seal is the correct size?  Have you cleaned out the place where it goes in the lower assembly, making sure there is no gunk (like old RTC) or barnacles?  I've changed mine many times and the seat is not a super tight fit.


--
Kent & Iris
KRISTY
SM243


Bill Kinney
 

Kent,

By far the best way to service the bow thruster is to remove the back plate, and that lets you remove the shaft, bearings and gears out through the BACK of the lower unit.  It lets you properly inspect the gears and bearings, make sure the inside is completely cleaned out of any debris or water and remove and install the lip seal the proper way.

The majority of SM bow thrusters I have taken apart have damaged seal surfaces from careless maintenance.  Given the difficulty of the repair of that damage, it is well worth the effort of babying these awesome pieces of equipment!

For those who do not know, there are 4 screws that secure the back plate of the bow thruster's lower unit.  As delivered from Amel these are countersunk, and then faired over with polyester body putty, so finding them takes a bit of paint removal and digging. When I reinstall them, I do not fill them all the way flush with putty.  Makes it a LOT easy to find them next year...



Once the four screws are removed, the shaft assembly and back plate can be pressed out, or gently tapped with a soft hammer.





Now you can remove the old lip seal the proper way with a proper tool and not risk damaging the housing with drills, screws, screwdrivers, or other make-shift ways of removing the seal.



Reassembly is the opposite order, seal first, shaft assembly next (after lubricating the seal lip with silicone grease), then backplate. Unless it is mechanically damaged during assembly operations, the o-ring in the back plate should not need replacement.  Lubricate it lightly with silicone grease before installation, and make sure everything is spotlessly clean.

Bill Kinney
SM160, Harmonie
Le Marin, Martinique


Paul Harries
 

This automotive video on lip seals may help you understand possible reason for failure.

https://youtu.be/WOfOHMI6Wnc
--
Paul Harries
Prospective Amel Buyer


 

The guy in the video is Kent Bergsma, a good friend of mine and the owner of MercedesSource.com (https://mercedessource.com/). 

I am sure there are plenty of people line Kent in Europe. In the US Ken is one of the best experts on older Mercedes automobiles. Since I have a 1985 300SD that I try to keep in very good condition, I speak to him often.

Bill

CW Bill Rouse Amel Owners Yacht School
720 Winnie, Galveston Island, Texas 77550 
   

On Wed, Jun 15, 2022 at 11:24 AM Paul Harries via groups.io <Pharries=yahoo.com@groups.io> wrote:
This automotive video on lip seals may help you understand possible reason for failure.

https://youtu.be/WOfOHMI6Wnc
--
Paul Harries
Prospective Amel Buyer


Steve Bell s/y Dusk SM378
 

Hi All.
I replaced the seals on my bow thruster approx 2 years ago same process apart from struggling to find the stews as matured it was an easy process.
On Bill,s recommendation at the time we ensured the replacement seal had the stainless steel spring as the old seal spring showed signs was badly rusting.

The one question I have is the time between replacing the seals we only use the bow thruster when entering a marina and with covid over the past two years our sailing time was curtailed somewhat.

How often do you replace the seals every 2 years or dependant on hours used.?

Regards

steve
S/v Dusk #378


James Alton
 

Steve,

   Bill knows his seals.  IMO a lot of the sealing with the bow thruster in the up position is done by the black foam donut seals that are in compression.  These take a set when compressed over time and lose some of their spring back so do not seal as well.  I think that the amount of time that this seal is in compression has a lot to do with when these seals need to be replaced and also how well they seal when you need them.  For myself, one thing that I do is to leave the bow thruster unlocked when the boat is dockside or in storage and save the compressive qualities of the seals for the challenging times such as beating to windward in big seas.  Not pinning the bow thruster of course introduces a new risk in that it is all on the lifting mechanism and the cable to keep the bow thruster up so I understand the reason for the locking pin so.  It seems that it is seldom the case with boats that an answer is  black and white.  

Best,
James Alton
Maramu #220
Marmaris, Turkey


-----Original Message-----
From: Steve Bell s/y Dusk SM378 via groups.io <stevect@...>
To: main@amelyachtowners.groups.io
Sent: Thu, Jun 16, 2022 11:46 am
Subject: Re: [AmelYachtOwners] Bow Thruster maintenance fail

Hi All.
        I replaced the seals on my bow thruster approx 2 years ago same process apart from struggling to find the stews as matured it was an easy process.
On Bill,s recommendation at the time we ensured the replacement seal had the stainless steel spring as the old seal spring showed signs was badly rusting.

The one question I have is the time between  replacing the seals we only use the bow thruster when entering a marina and with covid over the past two years our sailing time was curtailed somewhat.

How often do you replace the seals  every 2 years or  dependant on hours used.?

Regards

steve
S/v Dusk #378






karkauai
 

 Thanks, Bill K.  I hadn't heard that before.  I'll check it out when I service the BT next week.


--
Kent & Iris
KRISTY
SM243


Eric Freedman
 

I have changed the bow thruster seals about 12 times and rebuilt it once.

I have never had to take apart the bow thruster to change the shaft-propeller seal.

 

Except when I had to change the gears and bearings inside.

 

I push it in manually with silicone lube on the inside of the seal and on the shaft, and sealant on the outside.

It doesn’t hurt to use some very fine abrasive paper to gently clean the inside of the hole for the seal and the shaft itself.

 

Once carefully inserted I use a small PVC coupling to drive it in.

I also use a piece of PVC pipe to seat the seals on the prop shaft.

 

I use 2 foam seals inside and 2 outside on the bow thruster.

 

You can change the lip seal on the thruster shaft and the foam seals that are inside of the boat without removing the bow thruster.

Just put a hose clamp on the shaft tube and drop the bow thruster.

It takes a little manipulation, but the lip seal and foam seals can be changed in the water.

 

One person years ago abused his bow thruster, before the anti-torque plate was installed .

He left the boat and left the country. He did not install the pin. While at anchor without the pin in place

the bow thruster fell out of the boat and eventually due to wave action the boat sank, I believe in Grenada.

That is why Amel says to close the drain valve from the forward compartment and close the watertight door if leaving the boat for an extended time.

 

Amel then sent us a kit to install the anti-torque plate.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

 

 

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

 

From: main@AmelYachtOwners.groups.io On Behalf Of Paul Harries via groups.io
Sent: Wednesday, June 15, 2022 12:24 PM
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Bow Thruster maintenance fail

 

This automotive video on lip seals may help you understand possible reason for failure.

https://youtu.be/WOfOHMI6Wnc
--
Paul Harries
Prospective Amel Buyer


Eric Freedman
 

I forgot to mention that I use lacquer thinner to clean the surfaces before I install the seal.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io On Behalf Of Eric Freedman via groups.io
Sent: Thursday, June 16, 2022 5:26 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] Bow Thruster maintenance fail

 

I have changed the bow thruster seals about 12 times and rebuilt it once.

I have never had to take apart the bow thruster to change the shaft-propeller seal.

 

Except when I had to change the gears and bearings inside.

 

I push it in manually with silicone lube on the inside of the seal and on the shaft, and sealant on the outside.

It doesn’t hurt to use some very fine abrasive paper to gently clean the inside of the hole for the seal and the shaft itself.

 

Once carefully inserted I use a small PVC coupling to drive it in.

I also use a piece of PVC pipe to seat the seals on the prop shaft.

 

I use 2 foam seals inside and 2 outside on the bow thruster.

 

You can change the lip seal on the thruster shaft and the foam seals that are inside of the boat without removing the bow thruster.

Just put a hose clamp on the shaft tube and drop the bow thruster.

It takes a little manipulation, but the lip seal and foam seals can be changed in the water.

 

One person years ago abused his bow thruster, before the anti-torque plate was installed .

He left the boat and left the country. He did not install the pin. While at anchor without the pin in place

the bow thruster fell out of the boat and eventually due to wave action the boat sank, I believe in Grenada.

That is why Amel says to close the drain valve from the forward compartment and close the watertight door if leaving the boat for an extended time.

 

Amel then sent us a kit to install the anti-torque plate.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

 

 

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

 

From: main@AmelYachtOwners.groups.io On Behalf Of Paul Harries via groups.io
Sent: Wednesday, June 15, 2022 12:24 PM
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Bow Thruster maintenance fail

 

This automotive video on lip seals may help you understand possible reason for failure.

https://youtu.be/WOfOHMI6Wnc
--
Paul Harries
Prospective Amel Buyer


Bill Kinney
 

Steve,

If the bowthruster hasn't been used much, wear on the shaftseal is likely to be minimal.  On the other hand, the replacement parts are cheap and it's about a half day of work.  So we service our bow thruster (and C-drive!) every time we haul out.  

For the past couple years, that has been every year. The foam seals compress independent of the amount of use.  The ones on top are only relevant when the bow thruster is down, and have never leaked for us.  The important seals are the ones on the top of the bowthuster lower unit that keep the open ocean out of the boat.

James Alton's suggestion of leaving the thruster unpinned at the dock or at anchor is a good one. Save those seals until they are needed!

Bill Kinney
SM160, Harmonie
Le Marin, Martinique


Eric Meury
 

i never left the bow thruster unpinned while at the dock and don't think its a great idea..   To relieve the pressure on the seals leave the thruster pinned and just bump it lower.  It will rest on the pin and the seals will last .


On Thu, Jun 16, 2022 at 4:46 AM Steve Bell s/y Dusk SM378 via groups.io <stevect=yahoo.com@groups.io> wrote:
Hi All.
         I replaced the seals on my bow thruster approx 2 years ago same process apart from struggling to find the stews as matured it was an easy process.
On Bill,s recommendation at the time we ensured the replacement seal had the stainless steel spring as the old seal spring showed signs was badly rusting.

The one question I have is the time between  replacing the seals we only use the bow thruster when entering a marina and with covid over the past two years our sailing time was curtailed somewhat.

How often do you replace the seals  every 2 years or  dependant on hours used.?

Regards

steve
S/v Dusk #378






Bill Kinney
 

Eric,

What you describe is not the way the system was designed to work.  When the pin is installed it should be holding the weight of the thruster NOT the cables.  The lifting jack should not be compressing seals tightly, that's the job for the pin. In other words the pin is not just an emergency safety device, but is an integral part of the support system for the thruster.

The adjustment of the system should allow for the following procedure:
  1. Lift the thruster to the limit of the jack screw. At this point the pin can not be inserted, the thruster is a bit too low. The bottom seals should be just touching, maybe a couple mm compressed. In calm water, or at the dock the lip seal provides adequate leak prevention.
  2. With one hand squeeze the cables together.  This "sweats" the thruster easily up the last 3mm or so, compressing the seals.
  3. Install the pin.
  4. Release the cables.  The thruster will be supported by the pin, the cables will have a little bit of slack.
Although it is really hard to measure carefully, if you are using the double thickness of 10mm neoprene the total compression of that material for optimum life and sealing performance should be between 5 and 8 mm.  Squashing them dead flat will greatly shorten their life and add nothing to the quality of the seal.

There are three reasons for this procedure:

First, The height of the thruster can be adjusted much more precisely with the pin, instead of using the limit switches on the jack screw. This means that the compression of the seals is well controlled.

Second, if you are using the jack screw to compress the seals you are putting a higher load on it than it normally is called for.

Third, leaving the very heavy bow thruster with its weight carried by the cables and jack screw while pounding in a significant seaway also adds wear and stress to these critical parts.

Bill Kinney
SM160, Harmonie
Le Marin, Martinique


Eric Freedman
 

Hi Bill,

I adjusted the fixture on the top of the motor to compensate for the extra seal. The pin does support the motor

When the cables are squeezes together. This has worked for the last 80,000 miles including being in a hurricane.

 

When I was struck by lightning years ago, Amel sent me a completely new bow thruster with the bottom “v” section

separate.  This needed to be fitted and attached to the bow thruster. I adjusted the fit so that the thruster is flush with the hull.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io On Behalf Of Bill Kinney
Sent: Friday, June 17, 2022 2:48 PM
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Bow Thruster maintenance fail

 

Eric,

What you describe is not the way the system was designed to work.  When the pin is installed it should be holding the weight of the thruster NOT the cables.  The lifting jack should not be compressing seals tightly, that's the job for the pin. In other words the pin is not just an emergency safety device, but is an integral part of the support system for the thruster.

The adjustment of the system should allow for the following procedure:

  1. Lift the thruster to the limit of the jack screw. At this point the pin can not be inserted, the thruster is a bit too low. The bottom seals should be just touching, maybe a couple mm compressed. In calm water, or at the dock the lip seal provides adequate leak prevention.
  2. With one hand squeeze the cables together.  This "sweats" the thruster easily up the last 3mm or so, compressing the seals.
  3. Install the pin.
  4. Release the cables.  The thruster will be supported by the pin, the cables will have a little bit of slack.

Although it is really hard to measure carefully, if you are using the double thickness of 10mm neoprene the total compression of that material for optimum life and sealing performance should be between 5 and 8 mm.  Squashing them dead flat will greatly shorten their life and add nothing to the quality of the seal.

There are three reasons for this procedure:

First, The height of the thruster can be adjusted much more precisely with the pin, instead of using the limit switches on the jack screw. This means that the compression of the seals is well controlled.

Second, if you are using the jack screw to compress the seals you are putting a higher load on it than it normally is called for.

Third, leaving the very heavy bow thruster with its weight carried by the cables and jack screw while pounding in a significant seaway also adds wear and stress to these critical parts.

Bill Kinney
SM160, Harmonie
Le Marin, Martinique


Eric Meury
 

thanks bill,  I'll bring this up the the new owner and make sure he sees your comments.  


On Fri, Jun 17, 2022 at 2:47 PM Bill Kinney <cruisingconsulting@...> wrote:
Eric,

What you describe is not the way the system was designed to work.  When the pin is installed it should be holding the weight of the thruster NOT the cables.  The lifting jack should not be compressing seals tightly, that's the job for the pin. In other words the pin is not just an emergency safety device, but is an integral part of the support system for the thruster.

The adjustment of the system should allow for the following procedure:
  1. Lift the thruster to the limit of the jack screw. At this point the pin can not be inserted, the thruster is a bit too low. The bottom seals should be just touching, maybe a couple mm compressed. In calm water, or at the dock the lip seal provides adequate leak prevention.
  2. With one hand squeeze the cables together.  This "sweats" the thruster easily up the last 3mm or so, compressing the seals.
  3. Install the pin.
  4. Release the cables.  The thruster will be supported by the pin, the cables will have a little bit of slack.
Although it is really hard to measure carefully, if you are using the double thickness of 10mm neoprene the total compression of that material for optimum life and sealing performance should be between 5 and 8 mm.  Squashing them dead flat will greatly shorten their life and add nothing to the quality of the seal.

There are three reasons for this procedure:

First, The height of the thruster can be adjusted much more precisely with the pin, instead of using the limit switches on the jack screw. This means that the compression of the seals is well controlled.

Second, if you are using the jack screw to compress the seals you are putting a higher load on it than it normally is called for.

Third, leaving the very heavy bow thruster with its weight carried by the cables and jack screw while pounding in a significant seaway also adds wear and stress to these critical parts.

Bill Kinney
SM160, Harmonie
Le Marin, Martinique