Yamaha 115 4 stroke problem @ high rpm

[bud h]

I have a 2002 yamaha 4 stoke 115 on a Seapro 1900cc. I just changed the prop to a s.s. prop back in October. It ran fine for the last few trips, but last week while running about 5000rpm, it stopped pushing forward and the rpm cranked up to over 6000. I throttled back to 4000 and it picked up and kept moving. Tried again to get over 5000 rpm, same thing. Any thoughts?

[boats.net]

Sounds like ventilation or cavitation, check the prop make sure the back thrust washer is in place, and the prop is tight. If prop slides back on prop shaft enough the exhaust can come over top of prop instead of through and cause ventilation, the back lip of prop should go inside gear housing. You can check for prop slippage by marking a line across hub of prop and outside prop washer, run boat until slippage accurs and check the line across prop, if still aligned then prop hub is not slipping if misaligned then prop needs to be rehubed.

[bud h]

Thanks for the insight. I will check it out and keep you posted.