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Added
03/09/2004
Once
again it is time to tap into the great knowledge base of this list. My boat is
in need of a new exhaust system. The existing system is a water jacketed exhaust
pipe system. The exhaust header comes off the manifold and is enclosed in a
larger pipe (jacket) into which the water is routed. After approximately three
feet the jacket portion ends, the water exits the jacket and the exhaust pipe
continues without the jacket around it. From there the water and exhaust travel
through separate pipes to the thru hull for the exhaust where they are joined in
the same pipe so that they exit the boat together. Because of the way this
system is set up, the water would have to travel back up through a two foot loop
in the exhaust pipe and then up an additional five foot length of pipe to enter
the exhaust manifold. I believe
this
is why there is very little corrosion, if any, to the manifold after almost 35
years.
In
contemplating replacement I am looking at the possibility of using a
Vetus
waterlift muffler. The major issue I have with doing this is the fact that water
is injected directly into the exhaust relatively soon after exiting the
manifold. Even though I intend to inject the water after a loop between the
manifold and the muffler I am concerned that the moisture will work its way back
up the exhaust into the manifold and create corrosion. The reasons I am
contemplating a waterlift is because it will - supposedly be quieter, it will
not be as hot after leaving the muffler, and it will be considerably less
expensive. Does anyone on the list have any knowledge or experience that might
relate to this?
Most
small sailboats built today use a waterlift muffler, reliable, cheap compared to
a jacketed system. To get some idea of what is involved goto: http://www.yanmarhelp.com/i_exhaust.htm
and http://www.yanmarhelp.com this is a great website with a discussion forum
and tons of articles that apply to marine engines. The waterlift muffler if
installed and sized correctly blocks the flow of air into the engine from the
exhaust system. Also check out http://www.torreson.com I would guess that Vetus
would also have
instructions
for appropriate use of their products. Sashay has the original waterlift muffler
system from 1978 and all seems to
be well.
Unless
you have a backflow problem with the water, (in which your engine will be 100%
trashed) I don't think your exhaust manifold will be any worse for wear due to
condensation, especially on the inside. Most of the metal surface in there will
be dust-coated with carbon residue that will repel water. The stress of the heat
that the manifold goes through in standard duty will far outweigh any harm that
occasional condensation can do to it.
A
few years back I installed a new Yanmar and Vetus Exhaust on my boat.
Get the vetus and then follow the instructions carefully.
What you are