Engine Exhaust/Yanmar Problem - SailNet Community

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  #1  
Old 08-28-2001
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Engine Exhaust/Yanmar Problem

My 1984 Yanmar 3GMF has always been easy to start and reliable. Went to start her a couple of weeks ago and got nothing. Noticed seawater dripping from the air intake on the engine. The mechanic blew the water out of the engine and said he felt it was most likely a bad exhaust elbow, but possible a bad exhaust manifold or Vernalift. We decided to replace the exhaust elbow, but it still seems to be back-siphoning seawater. Next, we replaced the hose going from the exhaust manifold to the exhaust elbow (which was only slightly above the waterline) with a longer hose and vented loop. Still, the problem lingers. I am closing the seacock before shutting down the engine to blow out as much seawater as possible and then I have an easy start after opening the seacock. My oil and coolant appear very clean. One mechanic says it is most likely my exhaust manifold and that I should remove and test it (but also says it might be the Vernalift). Another mechanic insists it can''t be the exhaust manifold because I''d have water in my oil and thinks I should increase the height of the loop after the Vernalift in the engine compartment (it''s barely above the waterline -- but it''s been that way for 17 years and I have a very high loop at the stern). A service mechanic at Mack Boring said it sounded like a cracked head or cracked exhaust manifold or blown head gasket. He said I''d need to test the exhaust manifold and head on the engine -- without taking them off. I think if it were the head I''d have bad oil and or coolant. Another mechanic thinks it''s most likely the Vernalift gone bad. Are there any engine exhaust/Yanmar experts out there who can help a damsel in distress with this dilemma? What should I replace/test first? (Labor is so expensive I''m tempted to just start replacing things until it''s right/ does this seem like a reasonable approach?)
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Old 08-28-2001
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Engine Exhaust/Yanmar Problem

why don''t you call yanmars distributor and get to the engine shop they know the answers call 1-800-mack eng
that is mack boring.
eric
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Old 08-28-2001
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Engine Exhaust/Yanmar Problem

One of the fellows down the dock from me was telling me about a problem he was having and it was similar to yours. His exhaust outlet was barely out of the water also... And to make a long story short...he added a length of exhaust hose that raised the level of the exhaust to above the surrounding water and the problem went away.

Stange..but true....
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Old 08-29-2001
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Engine Exhaust/Yanmar Problem

Thanks for the input Rob...I''d be curious to know how long the boat had the hose low to the waterline before the problem developed. In other words, could a hose be low to the waterline for years without any problems and then all the sudden it is a problem? In any event, I think I''m going to buy a 180 degree return and 15" of exhaust hose to raise the loop coming off my Vernalift muffler about 18" above the waterline and cross my fingers.
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Engine Exhaust/Yanmar Problem

He didn''t mention specifically how long he had the boat before the problem made its presence known...but I get a feeling it was pretty much from the beginning. I''ll ask him when I see him next and let you know.
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Old 08-30-2001
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Engine Exhaust/Yanmar Problem

Hi long,

First of all, let me tell you that I''m not a a engine exhaust/Yanmar expert. Just happen to be in a similar situation with a 60HP Volvo MD-22. What should I replace/test first? (
It is quite difficul to asses your point without looking the instalation.

However you have been fortunate for the time being.

1. Has yor Yanmar decompresors? If the answer is yes, until you are sure that you solve the water intake issue, your should start cranking your engine decompressed. After a couple of turns, move the handles down, and fire the motor. This procedure will make you sure that you have expelled any water, not only in the manifold, but in the cilinders at worse.

2. Check where the water was coming from, wether from the coolant or seawater. (Just in case) In the first case, you may just have a burned gasket, particularly if there is any water in the oil.
Now, if you have experienced troubles in starting (as if your batteries were down),I bet you check the compression just to figure out any harm in the gasket.


3. As you said, if it worked for 17 years, it is hardly to believe any fault in the design instalation. It is funny. I thought the same in my boat. But the previous owner seemed he shut the water intake valve before shutting of the motor every time since. By the time I bought the boat, he indidcated that, but stated that he did so, "to keep jelly and fisdh away!!" Fool of me: I believe him.

4. Finally, at least for me, there is a very good and complete article in Sail Magazine of september 1998, addresing the exhaust installation.

Good luck
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