Engine revving

[richardsnowstar]

I have now found that I get similar problems with small angles of heel when motorsailing. The engine races or "hunts" and the exhaust smokes. It doesn't do this when simply motoring. Also the engine oil level has been dropping,

I have recently refurbished the engine head due to 2 of the valve springs breaking. I replaced all the valve springs and the 2 valves that were affected. The engine is a 27 year old Bukh but before the recent problem the engine had been very reliable and used virtually no oil. Also before I could keep the engine running smoothly at moderate angles of heel.

There is no turbo on this engine.

Has anyone got any ideas why this problem may have developed?

 

[macd]

Rule 1: if it's doing something different after changes, suspect the changes.
Valve guides/guide oil seals? Oil return from rocker gear OK? Would oil tend to puddle around them when heeling? Any idea why the springs broke?

 

[charles_reed]

In order of probability, assuming the engine was in forward gear:-

1. Worn oil-control,scraper rings allowing lube oil into the combustion chamber.
2. Sticky governor controls.
3. The prop acting as an additional force to increase engine revs.

 

[richardsnowstar]

Update:
The problems seems to be caused by the O ring on the breather under the rocker cover. This vents into the air inlet manifold so if any oil seeps through it goes straight into the engine with the air. When I refurbished the head I replaced the original O ring with one that seemed the right size. But I have now replaced this with an O ring supplied by Bukh and all seems well.