I'll Give it a Try
Your engine is not a turbo charged engine, wherein exhaust gasses drive the compressor blades. Instead, it is a mechanically supercharged engine, wherein gears drive the compressor blades.
The compressor blades pack air into the cylinders, and revolve several times faster than engine speed.
This means, when the engine suddenly speeds up or slows down, the rotating mass of the compressor blades receives a shock... just like if you stuck a board into the radiator fan of a car.
To soften this shock, Sea Doo installs a slip clutch in the compressor gear train, which depends on a washer to cushion the rotating forces.
If the washer breaks, all the pieces go into the oil pump and its engine repair time. Early engines had ceramic washers which did break. So they switched to metal washers and Riva sells replacement metal washers for overhaul.
Your seller says he 'maintained' the boat, but knows nothing about the supercharger, which needs to be overhauled every 100 hours. I submit he therefore did not maintain the boat.
if you buy the boat, make sure to inspect the supercharger drive and possibly overhaul it.
Simple as that.
