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Yanmar 1GM10 Exhaust Water very dark and peak 2400 rpms

Jim Oursler

New member
Recently got this old boat, a 1981 Santana 3030. Is not the original engine. At first all fine. Clear exhaust. 3300 rpm. Now exhaust water is dirty/dark. Max rpms 2400. Pulled off mixer elbow and it is clean except for soot. Found some diesel fuel on the mixer elbow gasket. Is not using oil. Is not smoking.
I am stumped.
 
Recently got this old boat, a 1981 Santana 3030. Is not the original engine. At first all fine. Clear exhaust. 3300 rpm. Now exhaust water is dirty/dark. Max rpms 2400. Pulled off mixer elbow and it is clean except for soot. Found some diesel fuel on the mixer elbow gasket. Is not using oil. Is not smoking.
I am stumped.
Am trying to attach photo (not attached, but you can email me for it [email protected]) of dark water that I collected directly from exhaust. Does not run rough. Bottom painted and prop cleaned about 30 days ago. Impeller replaced and was not deteriorated. Kept in freshwater. This boat had a broken mast... took the yard longer than normal to sleeve (about 2 months), so it has just been sitting at the dock. Every couple of weeks I would run it, first cranking without starting to distribute oil, then starting, running for a few minutes at low speed, then high speed in gear for 5-10 minutes as I know the engine needs a load for proper maintenance. Right now this is a major source of lake pollution. I always look at exhaust after starting to assure water flow, which is why I know it went from clear to dark/dirty. Put a 1/2 gallon of exhaust water in a bucket and photograhed it. Very little oil on top. Was going to run for an hour tonight, but afteer 10 minutes water temp alarm went off.
 
Am trying to attach photo (not attached, but you can email me for it [email protected]) of dark water that I collected directly from exhaust. Does not run rough. Bottom painted and prop cleaned about 30 days ago. Impeller replaced and was not deteriorated. Kept in freshwater. This boat had a broken mast... took the yard longer than normal to sleeve (about 2 months), so it has just been sitting at the dock. Every couple of weeks I would run it, first cranking without starting to distribute oil, then starting, running for a few minutes at low speed, then high speed in gear for 5-10 minutes as I know the engine needs a load for proper maintenance. Right now this is a major source of lake pollution. I always look at exhaust after starting to assure water flow, which is why I know it went from clear to dark/dirty. Put a 1/2 gallon of exhaust water in a bucket and photograhed it. Very little oil on top. Was going to run for an hour tonight, but afteer 10 minutes water temp alarm went off.
No water in the oil. Here is link to page with photo of exhause water. http://forums.sailboatowners.com/in...-exhaust-and-only-2400-rpm.181955/#QuickReply
 
to attach, use advanced editor.

Sounds like a fuel delivery issue.
If I recall this engine can be gravity fed or may use lift pump; either mechanical or electric. Which method is in use?

If you can use a different fuel source and fresh fuel you should be able to eliminate contamination as part of this.

FWIW; 2 months on the hard should have been a non issue for this engine. Many sit 6-9 months with no ill effects.
 
to attach, use advanced editor.

Sounds like a fuel delivery issue.
If I recall this engine can be gravity fed or may use lift pump; either mechanical or electric. Which method is in use?

If you can use a different fuel source and fresh fuel you should be able to eliminate contamination as part of this.

FWIW; 2 months on the hard should have been a non issue for this engine. Many sit 6-9 months with no ill effects.
I am going to dump the whole 12 gallons of diesel at a friendly auto repair shop. Will be a few days before I have an update. Will check into status of fuel delivery. Will replace the one, 1, fuel filter.
Thanks for the help.
 
I am going to dump the whole 12 gallons of diesel at a friendly auto repair shop. Will be a few days before I have an update. Will check into status of fuel delivery. Will replace the one, 1, fuel filter.
Thanks for the help.
Replaced fuel filter (only one on this engine and none in line). Replaced diesel fuel and cleaned tank. Same problem. Removed remains of air filter. Max RPMs around 2600. Black sludge coming out with cooling water from exhauset. Removed oil filler cap and can discern noticeable air pulsing, compression being blown past the rings. Should I tear this down, or get a re-built engine?
 
May have discovered the problem. While once again checking the mixing elbow, I noticed that the inside of the exhaust hose is blocking 20-25% of exhaust. Will get new hose tomorrow. Standby.
 
May have discovered the problem. While once again checking the mixing elbow,which looks almost new, I noticed that the inside of the exhaust hose is blocking 20-25% of exhaust. Will hopefully get new hose tomorrow. Standby.
 
well now you are just torturing us. :)
I checked the mixing elbow again. After replacing exhaust hose, cleaning fuel filter ( was only the one on the engine) and replacing all diesel, still 2400-2500 RPM with black sludge out the exhaust. Good water flow out. REplaced impeller a few months ago and again visually inspected it. Ran tonight for 10 minutes at 2400 RPM, no overheat, but a trace of black smoke. Expect it to be the rings allowing blowby and black exhaust water and some black smoke. Will call diesel mechanic cause I don't want to tear into the engine.
 
I have the same problem, more or less.
I hope its an easy fix as my motor is newly reconditioned.
Will start a new thread to see if anyone can help.
 
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