I have been running my boat with 454's for about 3 seasons in fresh water. The boat originally had 454 425hp kamma set up. It has been upgraded to upper 400hp range. Now, the owner before me said his engine builder did not recommend thermostats. I have never heard of this. It seems to me that it would run more effeciently with the engine temp around 150 degrees.
Currently the temp guages stay burried below 100 degrees. Should I install thermostats? Thanks for any input on this subject.

You need to run at the minimum a 140* t-stat. the cylinder walls will wear funny if u don't due to hot pistons/ combustion temps and cold block surfaces. Also your oil temps won't get up to 220* to burn off condensation. Optimun hp is made around 180-190*.

I would also say yes you need a thermostat.

I would run a 140. Only engines with extreme cooling needs like supercharger engines should run without thermostats.

My '84 302 kaama didn't have thermostats in it so i put some in. Cuts down on the wear and tear on the engine parts,most engines are designed to run at a min. of 160 degrees. Mine is a lot happier with them.

Can you run a thermostat with a crossover without a bypass if so any special things you need to do to it like drill holes in it.

I run a crossover and I drilled (3) 1/8 holes to smooth out the pressure when the stat opens and closes.

Thanks for the input guys! I need to take a look because I am also running a crossover. Right now after running at WOT for a bit of time I can shut engines down put my hand anywhere on the block and exhaust and it is only a little warm. I will try a set of themostats this spring see how it works.

patriyacht, is that a crossover without a bypass or with.

You will need a by-pass for the water when the thermostat is closed. Keeps manifolds cool and water pressure with in reason when thermostat is closed. You will want a couple of small holes in thermostat to help with any air pockets and help even out temperature spikes from thermostat opening and closing. I would suggest checking your water pressure during set up and testing also. Can save you from headaches later. Just my .02