Exhaust water coming back into manifold!!!!

[ricglobe]

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!

[ndutton]

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.

[ricglobe]

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.

[ndutton]

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.

[ricglobe]

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?

[ndutton]

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?

Yes, that is correct. A waterlift exhaust system requires exhaust pressure to lift the water in batches and expel it out the exhaust.

Was it ever an original universal part?

Nope, not to my knowledge.

[hanleyclifford]

We have had a couple of members report problems similar to yours with similar "mixers". In every case the so-called mixer had to go.

[ricglobe]

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???

[ndutton]

Do you think this accounts for the previous owners thoughts about opening and closing the thru hull???

Indeed I do. We see time and time again owners working around a problem rather than fixing it properly. For anyone wondering if that was a double entendre', you betcha

[hanleyclifford]

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???

Yes. Your mixer is actually a defective, non solution from the get go; the relationship of the engine to the water line tells you this. Your riser should "rise" as high as your boat configuration will permit.

[hanleyclifford]

Indeed I do. We see time and time again owners working around a problem rather than fixing it properly. For anyone wondering if that was a double entendre', you betcha

Droll, Neil - tres droll.

[JimG]

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.

[hanleyclifford]

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.

It is always a good idea to get the engine running first but the raw water valve must be opened at once when the engine starts. That means seconds, as in single digit - my rule is no more than five. The rationale for shutting the valve before turning off the engine is that in many cases the procedure clears the water lift to some extent and creates a margin of error, if you will, for the next start. I know of no practical way to substantiate that "bubemeiseh".

[ArtJ]

Those boats, like the Tartan 34C which have a standpipe do not have
the issue with long cranking times. I believe this is inherent in the
standpipe configuration and can be cranked for long periods if necessary.