Stuck and Broken exhaust valves

[gone2ddogs]

Since I did a valve job on my A4 6 months ago everything was working great until last weekend when It wouldn't start. Diagnosing the problems I found #3 exhaust valve stuck and #4 exhaust valve broken. Since talking to Don on the phone the culprit has been found to be water in the exhaust. The '59 Pearson Triton yawl has a cooper jacketed exhaust that I believe is original, but at the very stern of the boat there is some sort of muffler where the engine exhaust enters at the bottom and the water enters the top with both exiting overboard at the rear just above half way up the muffler. Anyone know what this is? It would seem to me that over cranking the engine or healing under sail would easily cause sea water to backup to the the engine. When this is mounted in the boat the bottom of the muffler is 6 to 8 inches above the top of the engine.

John
Triton #15

http://triton15.blogspot.com

[Kelly]

Hello John,

Your photo does seem to show a "mixing" type muffler where the exhaust gases and the cooling water are mixed before exiting the transom. I have a very similar system in my Cheoy Lee and you can go here on the forum to read a discussion and see pictures of the setup.

I would assume that like mine, your muffler is double-walled and that the gases pass through an inner-tube and are only liberated once near the top (near where the cooling water enters the muffler). The cooling water probably enters right over the end of the tube for the gases but the water is deflected by an umbrella-shaped "roof". The mixing occurs at the bottom of the muffler and the water+gases are forced out together through the exit by exhaust pressure.

So, all that is to say that before you get water in your engine from a normally functioning exhaust system of this type, you would have to fill the whole muffler with water before it could drain back down the central exhaust pipe. Your last run to the transom looks to be downhill so I would think that cooling water building up in the muffler from excessive cranking would simply drain from the muffler and run out the back.

Hope this helps.

Kelly

[gone2ddogs]

Last night I pressure tested the double walled exhaust and it held 30psi fine. I then setup the muffler section and ran water through it. Yes it's double walled and it looked like the water should run out the transom before it ever backs up the inlet. What is did find was that when I add water to the muffler I get a small stream of water back out the inlet that tells me there must be a hole or crack in the inner tube allowing the cooling water to leak back down to the engine.

Thanks
John
Triton #15

http://triton15.blogspot.com/