If you are able to run the exhuast up along a bulkhead to just under the deckhead ,then down to the opposite side from which it leaves the engine
, you'll have a pretty flood proof system, and out of the way as well.
If you exit it just about ten inches above the waterline , then use an elbow
to turn the last bit down below the waterline, on threads so it will swing up if it hits anything, you won't need a muffler
. You'll need a 1/4 inch antisiphon hole in the elbow
. I used this system on my last boat with a dry exhuast for ten years . It worked well.
Friends with wet exhuasts corroded out two engines since 1998 from condensation
on the valves etc. They are going for a dry exhuast now.
A diesel mechanic
in Port Townsend was quoted as saying" If everyone went for dry exhuasts and keel cooling
, we'd all be out of work."