Join Date: Apr 2006
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"His reasoning for this are two-fold: harder for seawater to enter in all but the worst conditions and (2) to be able to smell the warm air coming out of the engine room. Don't want to smell it; don't want to feel it."
Life is full of compromises. Ordinarily I'd say to trust the designer...but if they only gave the engine a 1.5" hole to breath through, I'd have to rethink that trust.
Without seeing the boat...there are often two vents into the engine spaces. One facing forward, the other facing aft, so there's always some pressure difference between them contributing to ventilation. Seawater should not be a major issue unless you are waverunning. One vent opens high in the engine room (the exhaust) and the other drops down low (the intake) so it is vented from bottom to top as well, contributing more to the cooling. And there would be an extraction blower in the exhaust vent.
Short simple runs are also of some value, so the question is, what are two reasonably dry locations with reasonable short pipe runs that can make this work for you?
On many sailboats both vents are simply mounted on top of the transom. I can't see your location being any more likely to ingest seawater than those are. If you're taking green water...there should be some provision to close off those vents, i.e. pull the intake hood and snap in a deck plate as part of your foul weather checklist. When you do that, you can open up a separate deck plate [sic] to let the engine room breathe from the main cabin. That's a reasonable compromise all around, and only requires buying one more 4" deck plate and cutting one more hole.