Engine Shut Off

Over the years I have had problems with the electric shut off button for the Yanmar 3HM35F. The problem has been that at times it works (usually when the engine has not been running long) and at other times it does not (when the engine has been running for more than an hour). When this happens the fix has been to clean the ground wire connections on the shut down solenoid. I recently went as far as to replace both of the terminal connectors on the ground wire. This time the problem has not been solved. My next move would be to replace the connection for the hot side and on the control panel. Since it does work sometimes, I don't believe that I need to replace my solenoid. Any other thoughts out there? Anyone else have a similar problem? It seems odd that it is only a problem when the engine has been running a while.

I had the same problem with the same engine HM 35F
I just got tired of fixing it and replaced it with a manual shut off cable
- ran it back thru the starboard locker..

The problem I had with mine was the wire was catching and bending up a little with a hard spot where there is a loop guide and actually adjusted too tight causing the wire to bend a little each time.

You probably have already checked this, but suspect the momentary stop switch on the panel. It may have corrosion or dirt in it...
Next disconnect the solenoid and run a jumper and activate it a number of times. Check the throw is the same every time and complete to throw the shutoff valve to it's stops without the wire bending.

Yanmar uses the most simple means with single throw solenoid on that engine to pull the fuel shutoff at the Injection Pump as opposed to other more complicated methods like timers and relays or always off until you turn the key to the on position and turns on the valve, spring throw, double throw... I never understood why they try and make something so simple so complicated sometimes.