Sorry to bring this topic up again, but I thought I should share our recent experiences on the issue...
We have experienced seawater backflow twice this year while on multiday passages in the South Pacific. The first time, we were unaware of Amel's suggestion to run the engine while sailing. The second time, armed with the knowledge that one should run the engine once a day, we had a crankcase full of seawater after 18 hours. It's now clear, as explained by Oliver, that under certain conditions, the running of the engine needs to happen more often.
Because we have a 1990 SM, there doesn't seem to be anything in the exhaust line to block/baffle/slow down sea water from backflowing toward the engine. We also have a stainless muffler without a drain. The old Perkins Prima M80T, still alive and well, may have survived simply by being old and worn, allowing the incompressible seawater to escape around the rings before bending any rods, blowing gaskets, or cracking the engine...?
At any rate, wouldn't the simplest solution be one that prevents seawater from entering the crankcase altogether? To me, the variables involved in deciding when and how often to run the engine are more complicated than something more bulletproof, like a valve. One has no way of knowing really how much seawater is being pushed up the exhaust in a given seaway. Let alone the fact that we are burning diesel for the sole purpose of producing exhaust gasses.
All that considered, I don't yet have an ideal solution. A muffler with a drain would probably cover it. Then depending on the passage, one can decide to pull the plug or to run the engine at certain intervals. For us, we will probably run the engine every couple of hours in a rough sea until I add a drain to the muffler or come up with something better. An engine full of seawater is a terrible thing to experience while making landfall after a long passage... I'm just grateful the engine survived and that we were carrying enough fresh oil.
If I do come up with a simple and "bulletproof" solution, I'll be sure to report back.
Mike & Hannah
On Mon, Jan 13, 2020, 9:10 AM CW Bill Rouse <brouse@...
Thanks, Scott. I agree completely
On Sun, Jan 12, 2020 at 2:46 AM Alan Leslie <s.v.elyse@...
Agree, seems quite a few of us are on the same pages on this KISS
Elyse SM 437