I replaced the pump bearing in my jacuzzi WJ. took it out to elsinore for a test run. Initially there was no noise. After a run across the lake to the cove I heard the rattle noise come back. I only hear it at idle which is at 1000 RPM. If I give it just a little gas to 1100-1200 RPM the noise goes away. Are these bearings known to make a little noise? U joints are about 3 seasons old with about 5 trips per season.

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Just your shaft spline and the drive line have a little clearance, at idle there is a little slop, given a little throttle tightens them up and noise goes away, common

I just recently did the same thing did a complete pump rebuild and i hear a rattle kinda vibration in 1300 rpm gas and boats rans real hard....i hope its common

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Driveshaft alignment too close or way off will also cause drive line talk...

Really bad with a stainless.

The raceboat used to sound like we were pumping rocks at anything below 900 RPM, the nasty cam in the race engine made it much worse. Our solutution was to make it idle at 1,500 RPM...

GT