1999 C115 cooling problem

I am experiencing cooling problems over 3500 rpm. I replaced the water pump and thermostats and the problem got worse than before. I saw quite a bit of water coming out over the top of the lower unit on the outside that I had not seen before. Would this indicate that the pressure relief valve may be hung open starving the powerhead for water? I pulled the new thermostats and ran it in the hose and it seemed to work OK but that is not the same as running hooked up out fishing.

Where is the pressure relief valve located? I need to check that and replace it I think. If I run without thermostats will the water pressure be too low or is it more important to have a good volume of cool water thru the heads? I live in S. TX so running in real cold water is not a problem. I would rather run with the thermostats in place as designed.

Any help / guidance would be greatly appreciated.

[jb123]

http://www.boats.net/parts/search/Ya...202/parts.html

its not labeled prv but it it right under the cyl banks, look for a large diameter hose running from it to midsection.

replace the parts with the new style.