20 kw ONAN Engine Kick Back on Shut Down

[Passages]

Scratching my head on this new ONAN gremlin.

Whenever I shut it down, the engine kicks backwards just before coming to a stop. Next start up, the belt slips and will not engage the raw water pump due to the impeller blades being bent in the wrong direction.

I've tried tightening the belt until I'm blue in the face but the belt slips unless I loosen it first, manually reorient the impeller blades, and retighten the belt.

Anyone see this before?

[Bob Bradley]

Are you shutting off the breaker so it's not under a load before shutting down?

[Passages]

Are you shutting off the breaker so it's not under a load before shutting down?

Yes, always let my genny cool at no load 3-5 minutes before shutdown.

[Captain Ralph]

IMO, it is normal for an engine to settle between compression strokes, sometimes turning a few degrees backwards. Some lungs may still be wet and stop regularly in the same spot.

There is an issue if the raw pump will not turn back and rotate normally when re-starting.
Rust or poor contact surface in the pulleys.
Worn, Poor fitting or wrong belt.
Over tension is not the fix, friction is.

[Passages]

Let me check my maint log to see how old the belt is.

Update: belt is 18 months old with 185 hours on it. Appears to be in good condition. Go figure.