Shaving heads

[Merc 2.5]

So when or how much cutting can they take b4 the water channels around combustion chamber start to be a problem? Say you start with a 38cc or bigger head and cut em down to 32 or 34cc ( 150psi) where would one start running into cooling issues?

[rock]

Don't know why there would be any issues. An open deck block with water circulating thru the head.

Rock

[25two.stroke]

Oh you can cut a lot. You can cut them flat till they get down to like 21cc and still be far enough away from the water passage to run them. The problems come when you blow em up so many times that your CC gets so tight you gotta start boring out the chamber pocket to get volume back...thats when you can get close to the water passages.

[Merc 2.5]

10 4. Reason I ask. I been chasing "hot" head temps all season long, ive changed ,cleaned new parts and gaskets everywhere, 2 different lowers to no avail , I pulled out some stock 2.0 150 heads and stuck em on the 2.5 and what do u know. Temps r gone runnin 125-135 on plane depending how hard im runnin, long idle out no wake 150 max. Head temps that is. It was upwards 170 180 and would get there quick. But head gaskets r good. Warped head or something? It was both sides also545323

[25two.stroke]

How do you have the faria temp sensor mounted in the head?

[Merc 2.5]

How do you have the faria temp sensor mounted in the head?

I have 2 stock mercury head temp sensors in. They were reading accurate with infared and tried another guage and another sensor. All read consistently. Prob is fixed now. Im at 125 130 on plane unless wfo then maybe 145 depending how long I hold it may reach close 150. Idle temps r normal again and it takes alot longer to reach operating temps, b4 the swap temps come up fast and my water pressure is better. I pulled old heads 3 or 4vtimes this season and blowed thru all passages ,was clear everytime and ive never had impeller come apart and always fresh water