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

Typically done with two outlets or tips as they are called. With the alpha
the simplest transom outlet point is right above the pwer steering. Make
sure you have clearance below the swin platform if you have one.If you want
to outlet below the power steering you will need several elbows. The
minimum install is a set of tips and some 4 inch exhaust hose to connect the
risers to the tips. Get tips with internal flappers and if you want extra
insurance get the straight cut tips and you can put external flappers on the
outside too. There is a different gasket for the connection between the
manifolds and the risers that will isolate the manifolds from the risers so
you can cool the manifolds with the closed side. Make sure you get a system
that includes capacity for the manifolds as they generate a lot of heat.
You will have to remove the plugs on the top of the manifolds to add
outlets. The plugs right in front of the risers. They can really be hard
to get out. There is a plate that replaces the Y pipe, you will have to
remove the engine to get the Y pipe out and put the plate on. If you want
mufflers you can get simple ones that go inside the tips. Theay are not
very effective. If you want real lift mufflers you will have some exhaust
plumbing to do. Straight exhaust even with mufflers in the tips is quite
loud. There may be some inline mufflers that will fit between the riser and
the tip, check the west marine catalog. You just don't have a lot of
distance between the riser outlet and the transom for much muffler. It is a
good deal of work and can be any where from just a bit louder to very loud
compared to your thru prop exhaust.

"Tan PS" wrote in message
...
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