2 replies to this topic

[lwg1214]

I have a 1998 sporster after about 30 min. of running it slows to a crawl. the rpms on the engine are high, but it will not go. the intake is clear. it's like you put the clutch in on a car while going 60 mph. any suggestions?

[RFoster130]

Sounds like cavitation. The engine revs, but it is sucking air as it is pushing the water through the propulsion system. Usually the wear ring in the pump is the problem. It gets worn down as you suck up sticks and rocks. The odd part though is, you say it does it after 30 min. Time should have no effect. Put the boat in the water and try to go full throttle from a dead stop. If it revs up but you dont take off, thats cavitation.

[lindstrom]

Sounds like cavitation. The engine revs, but it is sucking air as it is pushing the water through the propulsion system. Usually the wear ring in the pump is the problem. It gets worn down as you suck up sticks and rocks. The odd part though is, you say it does it after 30 min. Time should have no effect. Put the boat in the water and try to go full throttle from a dead stop. If it revs up but you dont take off, thats cavitation.

I HAVE A SIMILAR CAVITATION PROBLEM....BUT HAPPENS ALL THE TIME. HAD MY 1996 CHALLENGER ENGIEN COMPLETLY REBUILT LAST FALL.... USED IT ONCE ANT IT RAN FINE....NOW THIS SUMMER, I HAVE ONLY HAD IT OUT THREE TIMES, (2 TIMES TRYING TO DIAGNOSE THE PROBLEM) BUT HAVE NOT BEEN ABLE TO GET IT UP ON PLANE. TOTAL CAVITATION. I'VE BEEN TOLD THE WEAR RING IS FINE AND THE ENGINE RE-BUILDER PUT IN A SKAT PROP? ANYWAY, I WAS THINKING IT WAS SUCKING AIR FROM THE ENGINE COMPARTMENT (PAST THE GRAHPITE SEAL AROUND THE SHAFT. ANY BODY HEARD OF THAT HAPPENING?