YSM-8 bogs down under load.

After a rebuild by a licensed mechanic, my YSM-8 runs well, in neutral. however, as soon as it is put in gear it bogs down to the point of stalling, despite opening the throttle to full. In neutral the revs spool up and down in synch with throttle adjustments, the motor seems to run fine until put in either reverse or forward. The shaft is free and turns easily by hand. The mechanic is very good at scratching his head and saying that he does not know why this is happening. Any suggestions or ideas would be very much appreciated. Thanks.



Brooke

I've struggled with two different Yanmar models with somewhat the same troubles. Replaced everything with no improvement until a wise diesel dealer told me to check the nice shiny cast iron exhaust / water mixer fitting. The old one had corroded down to less than a 1/4" hole; the engine had been choked down to a 'pinhole' and of course it could put out no power. A new mixer and all was well. Take the thing off and peek inside to see if the mixer could possibly let any exhaust gas through. Worked for me.

Harry

also recheck the timing of the injection pump