Hi Bill, I'm not experienced at boat exhaust systems but since I've been reading up on them a little, I'll chime in and hope someone with experience can address this too. According to Calder and Gerr, most sailboats are water
cooled, with raw water injected into an elbow
coming out of the exhaust manifold. This transitions to a hose that is rated for wet exhaust systems such as SAE J2006 or UL 1129. Amongst other standards, this means the hose is rated for at least two minutes of operation with the water supply removed (not indefinite operation). A vent loop is provided. The hose enters a water lift
type muffler and carries the exhaust gas and the raw water with it. Pressure forces the gases and water out of the muffler output and out to the outtake through hull
. Your existing systems seems different. Your exhaust would have to be a dry type exhaust with stainless exhaust pipes leading to a dry muffler as exhaust hose is not rated for dry exhaust. If it is a dry exhaust system, then why would it have water injection just before the through hull
I recommend Boat Mechanical Systems by Dave Gerr for a good discussion of different ways to design and install boat exhaust systems
Boat Mechanical Systems Handbook: How to Design, Install, and Recognize Proper Systems in Boats: Dave Gerr: 9780071444569: Amazon.com: Books
There are some ways to significantly screw up when building or rebuilding a boat exhaust system so it's a cheap
investment to buy a good book or get professional advice
. For instance the size of the muffler compare to the volume of the outlet hose and the position of the water injection fitting to avoid flooding the engine
with raw water. The hose diameter, length and number and type of bends is important for controlling back pressure.
If anyone who actually knows about this stuff is around, feel free to jump in!