Hey everyone exhaust question here... I've had a few atomic four engines and this is a new problem for me. The previous owner instructed me to not open the raw water intake until after I had run the engine for a few minutes and to close it before shutting down the engine or I would get water backing up into the manifold.. I thought this was strange and probably not right but if it got me home I'd look into it later. No such luck. After an hour of running her I found water in oil. I've read the other threads and followed dons advice about flushing a few times and had good results although I still seem to be getting water backing up the exhaust. I've attached a few pics and read the other threads about this riser. Should I just scrap it and go with the traditional 12 pipe rise with the water entering on the back side. Is it an issue with the muffler positioning. If there is something obvious I'd love to know. Also, this engine is both fresh and raw water cooled... As well as running a hot water heater. I should also probably ad, she runs great! And temp stays at 150.... I'm lost!
Exhaust water coming back into manifold!!!!
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I think your mixing elbow is suspect and as far as I know there's no way to test it. I'll bet it has an internal breach.
If correct you're in the market for a new hot section. You can either replace the elbow or fabricate a hot section of black iron pipe like most of us. There is a wealth of information on the subject in the forum archives.
After that I'd say you're also in the market for a new raw water impeller. Running dry for a minute? Not good.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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I've done a few tests.... Ran the engine with the elbow disconnected from both the manifold and the muffler and it flowed down the correct side. As soon as I put it on the muffler it packed up(probably from lack of pressure from the exhaust). Why would the intake raw water need to be off to prevent water entering? I agree with the comment about the impeller although at the moment it's pumping water great! A new hot section may be the only next step.
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With that new information you open up the possibility of exhaust system backpressure contributing to the problem. It can be due to a variety of conditions including internal muffler debris or an internally collapsed exhaust hose. Are you able to reach full expected RPM?
Here's a peek at the inside of the mixing elbow.
Last edited by ndutton; 08-03-2014, 09:04 PM.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Yes, I am able to reach full rpm. Would I be correct in assuming that if the elbow was connected to muffler and not the manifold exhaust the back up if water would be from lack of exhaust pressure? Thanks for the pic of elbow... I'm pretty convinced thT piece needs to go. Was it ever an original universal part?
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Originally posted by ricglobe View PostWould I be correct in assuming that if the elbow was connected to muffler and not the manifold exhaust the back up if water would be from lack of exhaust pressure?Was it ever an original universal part?Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Ya, I've been looking at the archives and that seems to be the case. The typical hot section has never had this problem, I've even seen another boat in my marina with this riser and problem. Thanks for the advice guys. As soon as I get her home I'll be switching her over. Do you think this accounts for the previous owners thoughts about opening and closing the thru hull???
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Originally posted by ricglobe View PostDo you think this accounts for the previous owners thoughts about opening and closing the thru hull???Last edited by ndutton; 08-03-2014, 11:51 PM.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ricglobe View PostYa, I've been looking at the archives and that seems to be the case. The typical hot section has never had this problem, I've even seen another boat in my marina with this riser and problem. Thanks for the advice guys. As soon as I get her home I'll be switching her over. Do you think this accounts for the previous owners thoughts about opening and closing the thru hull???Last edited by hanleyclifford; 08-04-2014, 08:35 AM.
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I read somewhere that if you have a long cranking time in starting the engine, you can pull water into the manifold. I've never had the problem, but I do close the raw inlet if I think it might be a long one, like after many weeks of neglect. Shutting it before turning the engine off seems silly.S/V Latis
Brookings, OR
Ranger 33
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Originally posted by JimG View PostI read somewhere that if you have a long cranking time in starting the engine, you can pull water into the manifold. I've never had the problem, but I do close the raw inlet if I think it might be a long one, like after many weeks of neglect. Shutting it before turning the engine off seems silly.
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