Cavitation and overheat.

[iwombat]

Motor: '77 85hp

So, I put my motor up one more peg and got some cavitation at WOT, holeshot and in the turns. Definitely one hole too high. Running at not-quite wot I overheated (overheat horn sounded). After letting it cool down I ran back to the launch at 1/2 throttle with no more issues, but it appears I blew a head gasket, at least judging from the sound. I'll check it out for sure tonight.

Anyway, the real question - can cavitation starve the water pump of water and cause an overheat, or should I be looking at something else as the cause? Pretty new impeller and I get good spitting out the exhaust reliefs.

 

[wilde1j]

Re: Cavitation and overheat.

If you get too high, the water pickup can be affected. Cav plate should be just uncovered @ WOT.

 

[iwombat]

Re: Cavitation and overheat.

That's pretty much what I thought. I just wanted some confirmation before I started suspecting my vernatherm or something else.

 

[tashasdaddy]

Re: Cavitation and overheat.

well if the pump was not picking up water, you need an impeller also.

 

[iwombat]

Re: Cavitation and overheat.

That's a good point, TD. Good thing I have a spare. I'll check pressure out the tell-tale after a head-gasket replacement. It was pumping some water, because it took quite some time to overheat. Probably just not enough to push the poppets out at high RPM. Anyway, I'm thinking the pump was wet enough to get lubed, but I'll give it a good check.