Sea Rayder F14 Jet Sport 120

[Tincansailor]

Hope I'm in the right forum, I have a 96 Sea Rayder jet boat with a Merc. 120XR Jet Sport. My problem is it starts out fine (a little Bow rise) but once it's up to speed after about 5-6 seconds it starts to Surge or cavitate? if I slow back down it runs again for a few seconds then spins up again. The Impeller looks good and the clearances look even with no unusual wear noted. The ride plate was not sealed well to the hull, a bunch of RTV. I have removed it and plan on replacing the seal (If I can find one). What else can cause this cavitation issue?

 

[dazk14]

You certainly can have pump sealing issues. When you say surge, that's generally the nomenclature for Fuel delivery problems.

Pump sealing tends to be most noticeable upon fast take-offs and ride plates on normal PWC are generally not sealed, but the pump shoe(big time) and intake grate are.

If the impeller is spinning in an aerated mix, the engine should easily rev quickly up to the rev limiter, although you won't be moving very fast.

Welcome to the forum!