Shuddering engine

[tidclacy]

Went out yesterday and found engine ok at tick over 850 revs, when put into 1250 to 1500 revs engine shaking but ok as revs were increased. Intermittent problem. Could it be a sticky valve spring? Have been out a couple of times already with no problems but have not used the engine much.

Yanmar 3mgf 28 hp.

Any advice welcome. Thanks in anticipation.

 

[No Regrets]

Diesel bug?

Worth running the engine for an hour or so at high revs to see if it just needs using, but check fuel filters if you suspect the bug.

 

[Concerto]

Check your engine mountings and shaft coupling. A loose mount or coupling may only vibrate at selected speeds. Also worth checking the engine alignment.

 

[chrishelen]

Fuel problems I would guess, change filters to start, have a look at the primary filter, if its full of slime you have the bug. If not make sure all fuel pipes are nice and tight as air getting in can cause intermittent running problems. ( how do I know this?)
Good luck.

 

[RichardS]

If it's only when the engine is in gear it might be something small around the prop. Found this out for myself last year.

Richard

 

[pmyatt]

Same engine, just been serviced and new fuel filters etc. In gear, no vibration up to about 2200RPM, but beyond that it increases steadily and at 3500RPM was wobbling the Admiral's wine glass - have been told to behave or will be replaced as Captain!

 

[chrishelen]

If it's only when the engine is in gear it might be something small around the prop. Found this out for myself last year.

Richard

Quite possibly, but I would guess a fuel problem as it happens under load in gear. Just a thought, might be an idea to check mounts, make sure they are tight.

 

[Topcat47]

Check your engine mountings and shaft coupling. A loose mount or coupling may only vibrate at selected speeds. Also worth checking the engine alignment.

+1