Yanmar engine cutting out

[KLBH]

I have a Yanmar 4JH4-HTE engine 2007 that has started intermittently cutting out when engaging gear or changing from forward to reverse, as you can imagine, this is not great when coming in to a berth. It will start again, no problem, but may or may not cut out again when a gear is selected. It is difficult to say for certain the conditions when the problem occurs (other than exactly when you don't want it to) as it is so infrequent, but my feeling is when the engine is hot and been running for at least a couple of hours.
The fuel filters are 4 months old and I have a fuel polishing system on board, all looks clean.
If anyone has any ideas or things to check I would welcome the feedback.

 

[jamie N]

Are the idle revs the recommended ones, or have they dropped slightly/imperceptibly?

 

[KLBH]

I am not sure what the specification is for the idle speed, but it's idling at around 800rpm and I have not noticed any change. I will check it next time out and see if it is different cold to hot. Do you know what the idle speed should be?

 

[Bilgediver]

Check that the idle speed is being determined by the adjustable slow running screw stop on the engine anD NOT by the teleflex which is not precise.

The stop is adjacent to where the Teleflex connects to to the engine speed lever.

 

[VicS]

I am not sure what the specification is for the idle speed, but it's idling at around 800rpm and I have not noticed any change. I will check it next time out and see if it is different cold to hot. Do you know what the idle speed should be?

See this extract from the service manual

 

[shanemax]

I had a yanmar.I spent more time with the tool box out and cleaning my hands than sailing.

 

[KLBH]

I've checked out the fast and slow stops, the idle speed was low at about 730rpm. Adjusted to 825rpm and engaged forward and reverse gears multiple times without problem. Hopefully that has sorted the problem, time will tell.
Thanks for all your help.