Re: Amel Bow Thruster Tool: a mystery leak?

Judy and Bill aboard SV BeBe <yahoogroups@...>


Two possibilities, based on what you said:
1.) Is it possible that one or more of the foam seals were in the wrong place. In a set of 3 seals. one is made of a substance that is different than the other two.

2.) Did you pin the bow thruster in the UP position as soon as you were finished with it?

When I have correctly done the above and serviced every 2 years, I eliminated the water egress.

BeBe, SM2k, #387

--- In, "Jose" <jvenegas@...> wrote:

Well, we do have a mystery here or what?
I would have agreed with Garry that the two seals on the bottom should do the trick, particularly if they are pressed against the flat fiberglass surface of the boat. However my experience tells me otherwise and I have had water coming in two out of the three years I have owned my SM2000 in spite of 3 full seal changes.
The first leak happened on the inaugural trip from Fort Pierce to Savanna. The previous owner had just changed all the 3 seals weeks before the sale. During the overnight passage we had no particularly large waves under a nice 15 knots reach. However, after I arrived to Savanna, I found the forward bilge had salt water almost up to the floor! Not the kind of thing a new boat owner wants to see after his first cruise. In the slip, I make sure the water was not coming from anywhere else, and that the boat was not sinking. Then, I changed the 3 foam and the lip seals and reduced by a half turn the length of the shaft to increase the compression to the bottom seals when the pin is in. Results: no more water for two seasons.

Last spring I first noted a small leak that increased progressively and, by the middle of the season, I was getting two good gallons of water in a trip from Boston to Province Town. After I saw with my own eyes that the water coming through between the lip seal and the shaft, I made an extra seal that I could wrap around the shaft, which kept the leak at bait for the rest of the season. I will be posting pictures of the seal because I think something like this should be on every Amel spare part box.
Any way today, with the boat on the ground, I took the thruster out and found that the (lip) seal around the shaft was, as expected, stretched. However, both the bottom and the top foam seals were absolutely intact. So Garry, this trashes the theory that the bottom foam seals, compressed with enough pressure, can prevent the water from coming in. Remember that I removed a turn increasing considerably the compression on the foam seals with the pin in.
Question for the forum: how can water get around the two bottom foam seals under good compression? The sealing surface from below looks nice and flat. For me this is a mystery.

--- In, amelliahona <no_reply@> wrote:

Hmmmm. Kent, there must be something fundamentally wrong here. I think we have both sailed many of the same waters and it just doesn't seem right that I have had no trouble in this area and you seem to have been plagued by the issue. I know I have sailed and or motored with some very significant pounding and still have had no water ingress. Is it possible that the seals have never been properly installed? Did you mention that there were three seals on the outside?

In the retracted state, the top of the bow thruster "anti-torque cap" (see picture #2 in the folder entitled bow thruster service) should compress the two rather dense neoprene seals against the roof of the bow thruster trunk creating a compressive seal against the shaft. In the extended position, the lip seal recessed into the trunk top and the foam seal attached above the lip seal should prevent water ingress. The shaft should be relatively smooth and not have grooves or ridges in it that would inhibit a good circumferential seal.

As a trouble shooting step you might place a large dollop of modeling clay on the top of the anti-torque cap next to the shaft, install the bow thruster, then retract the bow thrust, then remove the bow thruster and measure the height of the modeling clay to see if that distance is roughly the depth of the two external seals. Perhaps due to how your trunk was built or differences in the manufacture of the bow thruster itself, you aren't getting compression of the seals upon retraction.

The water in the oil is a leaking lip seal on the bow thruster prop shaft and is another mater all together. The sleeve previously describe, and depicted in some un-labeled pictures in the Photos section was indeed for the bow thruster prop shaft.

Just some thoughts,


--- In, karkauai@ wrote:

Hmmm. Have changed the seals (or had them changed) every year and its always leaked water into the boat. This is the first time I've had water in the oil. I'll try Erics silicone trick this time.
Didn't someone install a thin sleeve on the shaft, or was that on the main drive?
Thanks, your report is encouraging.
SM 243
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