Re: Sea Chest

Mark Pitt

I always run the anchor washdown pump for 20 seconds, turn it off, and then immediately turn on the generator or Yanmar.  Haven’t lost an impeller since I started doing this a few years ago.

Mark Pitt
Sabbatical III, SM419

On Nov 27, 2020, at 3:34 PM, Karen Smith via <karenharmonie@...> wrote:


I have taken the photos and annotated them with the parts list.  

All of the fittings I used are standard NPT pipe fittings.  In the case of the outlet fitting on the strainer, that is actually a female 1-1/2” BSP thread.  In this size, the NPT and BSP threads are compatible enough that they will screw together just fine, but they will not make a reliable high pressure seal.  Don’t expect “teflon tape” to help here.  You’ll need paste type pipe sealant.  For the very low pressures seen here, it works fine despite the small mismatch in thread shapes..

We have been running this long enough now, we can confidently say that it works with no issues. Well, no issues that were not already there with the stock Amel manifold.

Here is the only problem we have with the “sea chest” design.  As we sail, air is entrained under the hull.  Some of this air finds the sea chest thruhull and rises into it, displacing the water.  If we are sailing fast, enough air comes through that in a very few hours the strainer and standpipe are empty of water. I am pretty confident that needing to purge this entrained air is the primary reason that the generators on Amel’s have such short lived raw water impellers.  I have a couple of ideas on how to improve this situation, but nothing ready to implement yet.

Our new generator has a hair trigger on its exhaust temperature shutdown which has made this problem more obvious.  Occasionally, and only when we are sailing, the high exhaust temp triggers a shut down right after it starts.  A second start try and it runs fine. If I crack the lid of the strainer and purge the air, it never happens. 

Short of closing the sea cock, I can’t think of a way to keep the air out, so I am trying to figure out a way to easily purge it.

Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL, USA


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