I have a boat fitted Mercruiser I/O 5.0 V8/ Alpha I with the usual exhaust
manifold-thru prop setup. This is operated in sal****er and typically the
shutters, exhaust manifolds and elbows and exhaust pipe give way about every
3 years. This is quite a big ticket, especially with the exhaust pipe part
which requires the engine to be removed.

Using a closed freshwater cooling system can take the manifolds out of the
equation, but the elbows and exhaust pipe remain exposed.

Am thinking of putting in the closed cooling systems and using a thru-hull
exhaust system. This leaves only the exhaust elbows to contend with.
Easier and cheaper to maintain-yes???

Question is what do I need and how to go about putting in a thru-hull
exhaust system. For one, I will need the thru-hull exhaust outlet with its
flapper. Raw water will continue to be delivered to the elbows and mixed
with the exhaust at exit.

1. Do I need 2 outlets?
2. What is the mounting point of the outlets, at waterline, below or
above and by how much?
3. Do I need some kind of muffler/exhaust box or a direct connect to the
elbows will do?

Thanks in advance.

PS Tan