Smoke & Oil in Exhaust!

[Jim Haynie]

My 1988 Legend 37 with Yanmar 3HM35F has suddenly gone low on power (max RPM 2200) and emits thck black smoke and some black raw oil from exhaust when trying to motor hard under load. OK when at mooring in neutral, will go up to 3400 with only little smoke and no oil output. Is there ANYTHING other than the obvious worn-out, cracked, or sticking rings that could cause this symptom and can be fixed without remove/rebuild engine?? Anyone out there rebuild their own who can give me advice?? Heartbroken and worried.Jim Haynie

 

[Jim Ewing]

Prop

Have you checked that the prop is 1) clean and 2) doesn't have anything (line, bag, debris) wrapped around it.Jim"Prospect"

 

[Ron Hughes]

Call your local Yanmar guru

Yanmars should last for 20,000 or more hours before they need a rebuild. If you have a sudden change, call a pro and ask about it. They won't bite, and will probably put your mind at ease. There are experianced people here at this site, but you aren't talking about changing some little part on the boat, you're talking about the most expensive part in the boat! Call Yanmar! That's what OI'd do. Ron

 

[John K Kudera]

Black smoke

Hi,I just spent a lot of time and money to fix the problem I had.All the quick fixes,Pulled the boat, checked the prop for barnacles and other stuff, cleaned the fuel filters and intake filter, removed the exhaust elbow, cleaned that.Bottom line is I had to do a valve job. My boat just was not run at high enough RPM's to keep the valves from collecting carbon, and failing to seal.You can check if one cylinder is not working by doing this: Start the engine use the proper wrench and crack open the fuel injector feed lines on each injector, one at a time, if when you open the line the engine stumbles and tries to stall, that cylinder is operating properly. If when you bleed the injector, nothing happens, you have found the problem. If you are able, use the manual and remove the head from the engine and have it gone over by a machine shop that does autos or possibly a large garden tractor dealer that sells John Deere (they use Yanmar).If you are not mechanical, get a marine mechanic!J Kudera, s/v 50-50 H34