excessive smoke and oil slick residue in water

[Tim Farley]

yanmar sb8 black smoke in exhaust oil in water could beunburned fuel.neeed help (engine rebuild from top to bottom)any info on injector shims could help

 

[Dick Carey]

Black Exhaust Smoke

Tim,The black exhaust smoke is probably unburned fuel and may well be a result of a 'sooted up' exhaust mixing elbow (where the engine exhaust and the engine cooling sea water mix together before going out as a 'wet exhaust'. After 7 to 10 years they soot up enough that they should be replaced (both the elbow and the double ended coupling and the gasket weher the regular elbow bolts to the engine. Yanmar dealer can give specifics on parts.I replaced mine after 10 years use and fuel effeciency went up 25%, from 0.4 GPH to 0.3 GPH over a full season.Dick CareyS/V Puffinw/ Yanmar 2GM20

 

[Bob Rutland]

Black smoke

Black smoke is usally a sign of a diesel under stress. This stress could be internal(ie:mixing elbow)or external like a prop incrusted in barnicals or fowled.If you get black smoke out of gear, I would say it is internal. If you get black smoke only in gear, I would check the drivetrain, starting with the prop.Hope this helps, Bob

 

[Jim Vincent]

More Black Smoke

Dick, thanks for the info on the elbow,i'm also experiencing black smoke but only for 8 or 10 min. at first start. (idle power & in neutral) do you also suspect the elbow in this situation? take care, Jim Vincent, Toucan

 

[Dick Carey]

Elbow Inspection

Jim,Inspecting the elbow is one big pain in the ass. You have to remove the 90 Deg. elbow where it attaches to the engine exhaust port. You are now half way there to replacing it. If it's been in use for 7 to 10 years, the mixing elbow (not the 90 Deg. elbow) should probably be replaced. Whether or not you replace the mixing elbow, you will need to put on a new gasket where the 90 Deg. elbow mates with the engine.Dick Carey