It's almost certainly the mixer elbow.
I replaced it on my 2GM20F a couple of months ago. Take the manifold and the
elbow off as one. (You won't be able to separate them anyway.) There are
four bolts where the manifold connects to the engine.
A new manifold, elbow, connector and gasket cost me about $225 US. It's not
a difficult job, provided you have access.
As a temporary fix, try removing the water intake hose and using a coat
hanger to clear the passage. Even if this works, you still need to replace
the elbow.
Yes, you need water in the exhaust to avoid melting it.
Jack Brennan
Former C&C 25
Shanachie, 1974 Bristol 30
Tierra Verde, Fl.
-----Original Message-----
From: Dave Lane via CnC-List
Sent: Tuesday, May 20, 2014 6:17 PM
To: cnc-list@cnc-list.com
Subject: Stus-List Plugged exhaust - help!
Well, as things usually go, something that worked in the fall doesn't in
the spring.
The engine starts but no cooling water flows out the exhaust - I did not
need to find this out on launch day!
Anyway, this is a C&C 29-2 with 2GM-F engine. I diagnosed it and it's
fine all the way to and including the raw water out of the heat
exchanger. When I blow into the hose going into the u-shaped exhaust
mixer, it's plugged. The engine exhaust itself seems fine. After it goes
through the mixer, there is about a 2" ID hose to the muffler then
another 2" hose to the stern port.
This problem may have been getting worse as the years went by as last
year I was thinking the water flow was not as much as previous years.
Questions:
1. Is it likely that the blockage is in the mixer? Any suggestion for
what I should try next?
2. The mixer has a right angle elbow going into it - should I try to
remove it? Or stick I wire in it to try to unclog it?
3. In order to motor "slowly" home (a few miles) from the marina, I made
a run to Canadian Tire for "stuff" and I plugged the exhaust water input
to the mixer and made a temporary hose from the heat exchanger that I
could feed out of the cockpit locker and over the side (the water flow
was great). Can engine be run without water flowing through the muffler?
(ie. does it depend on water cooling?)
Thanks in advance,
Dave
St. Margaret's Bay, NS
"Vela" C&C 29-2
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