After I bought Ipanema 10 years ago we had two years of struggle trying to prevent the leak of water through the bow thruster. About 8 years ago we had a long discussion on this forum about the bow truster seals which I had changed several times following all the recommendations given by Amel, including adding a third bottom donut seal to increase the pressure. It was all at no avail. So, before our transatlantic on 2012 I came up with a brute force solution adding an extra removable sealing system that was wrapped around the shaft and had to be secured after the bow thruster was fully retracted. This worked very well during the trans Atlantic passage (not a single drop of water) and gave me the security of knowing that in addition of the sealing effect, the shaft was being held by one redundant mechanism.
As we came back to Boston, we kept using the method but it became very inconvenient to mount and dismount the contraption every weekend when we left and came back to Constitution Marina.
My interpretation of the problem was that due to uneven wearing of the surfaces that guide the bow thruster up and down motion, it resulted in a misalignment between the shaft and the sealing surfaces. This misalignment caused a small deviation of the shaft from the centerline which pushed the lip seal sideways and, because the Amel recommended seals are made of a hard material, it opened a point of water entry.
I proceeded to test my hypothesis and ordered two special seals made of silicone from a soft seal manufacturer (SSP Inc). It took several months to get them due to the small number of units I ordered (just 2) but, after I installed them three years ago, I had no more leaks and my bilge has been dry ever since. The cost for the two seals was $72.50 and, more importantly I have not had to change them or the donut seals since I installed them. I have checked them and the donut seals and they are all still in good shape.
As I am preparing Ipanema for our long term cruise, I am ordering a few spares to carry with me and I will be happy to order some extra ones for any body that wants to try them.
I missed taking pix before installation but here are pictures of them installed, before and after adding the top donut.
Jose Gabriel Venegas
Ipanema SM2K 278