more cooling problems

i had a previous thread about this i have a 83 blackmax 150 xr2. ok so here is what its doing. when you run it on a hose its fine and when your iddling its fine but after about a 2 min run at anything over 2k rpm it stops spiting water and it just shoots steam out of the pee hole. you can stop kill the motor fire it right back and take off again and same thing happens. ok so here is what has been done and checked. new waterpump, thermostats were removed, poppet valve checked (still looks new) water ports checked, even blown compressed air back through water system. my dad thinks it could be possibly cavitating somehow. is this even possible and if so how do you fix that. any other ideas what it could be it has me stumped i dont even knw where to begin looking.

Re: more cooling problems

ok did some more investigating and after pulling the foot again and took the water pump back off i noticed a missing gasket so i found the water pump box and it was there. this is the gasket that goes inbetween the base of the pump and the foot. could this gasket missing caused the problems?

Re: more cooling problems

Definitely

Re: more cooling problems

iight well figured i would post the findings on this problem. after replacing the gasket it still was doing it. i got tired and took it to the local shop and left it. the mechanic called today saying it is the base plate gasket. he said he has never seen a motor do this in 25years of working in a marina. hopefully sombody will find this info helpfull.