what is the true purpose of the blowoff valve

[brances toy]

on a 1996 225 oceanrunner what is the purpose of the blowoff valve between the thermostats? did the 1992 model connect with a hose tsat-to tstat.any help would be gratley appeciated.thanks brances toy.

 

[seahorse5]

Re: what is the true purpose of the blowoff valve

On Johnson and Evinrudes, the "blow off"valve is used above about 1500 rpm to bypass the thermostats and run water straight thru the engine block.

Thermostats control the engine temperature at low speeds to promote good combustion and a smooth idle. As rpms increase, comustion chamber pressures and temperatures climb and hot water around the cylinders is not needed, plus the now cooler water helps the heat transfer from the cylinder walls.

The valve allows for more water flow to help high speed cooling and to prevent the water pressure from getting to high.

 

[brances toy]

Re: what is the true purpose of the blowoff valve

Captain i had a 1996 powerhead gernade,i remaned a 1992 sb assembly had to reuse my 96 heads.the 96 block had a blowoff valve ,the 92 doesnot,though it does have a 1/8 pipe hole there.would it be ok to tee in here almost acting like a blowoff valve with the hole drilled in it ive read about here.or just run a hose from tstat to tstat.any thoughts and response would be greatly appreciated.thanks kenny(brances toy).