On motors that are producing more horsepower than they came from the factory, I'd at least run a 160deg. T-stat. I'd also raw water cool the manifolds. I feel that a good seawater pump with a thru-hull fitting is a necessity. Anyway I had experimented with a closed system on a slightly worked 454 mag motor. I ended up cooking the motor because the south bay strainer's holes were too big and the oil cooler got plugged with seaweed. I ended up building another motor without the freshwater cooling system. Also got a better strainer and even installed a Groco basket strainer in the boat. I flush every time with a Perco flushpro. No problems for 2 seasons.I also believe my Jabsco bronze seawater pump is worth the $250 it cost me. Even if you run in freshwater it's still a good idea to flush because of organisms and marine life that can plug up manifolds and wreac havoc! I would only run a 140deg. t-stat in salt water because the salt can crystalize at higher temps, and accelerate corrosion.
BBB

Audio added it to his boat. If you recall, he runs in the salt and would really benifit from it. I don't think he even got a season out of the system before he ripped it off. I can't recall the specific problem though.

I agree... your oil should be running around 200 degrees... it can go up to 250 without any problems.... 300 it starts to break down... I had an air cooled bike and the oil ran consistantly at 350... hot enough to deep fry chicken!

Just rebuilt my 500 EFI's. Ordered the system for $530 each motor. PM or e-mail me if you'd like the contact info. I don't have it on me at the moment to post.

http://i-netmarine.com/

I HAVE USED THESE SYSTEMS ON 3 OF MY BOATS AND NEVER HAD ANY TROUBLE.

thanks for the comments. what kind of motors did you put them on?

BOAT 1 350 ZZ4 MOTOR
BOAT 2 350 STOCK
BOAT 3 TWIN 454 BROVO MAG

ALL THREE WERE ADDED ON AFTER BEING RUN IN FRESH AND SALT WATER BUT WERE ALLI N GOOD SHAPE (SCALE RUST) THEY ALL RUN ABOUT 170 DEG.

The most reasonable price I found was from Ocean East Marine for CC. JIM
oceaneastmarine.com

Same here, that's where I bought mine.

Your engine internals will stay spotless (even aluminum heads and manifolds).Engine warms up quicker as well.If you are running aluminum manifolds I would leave the raw water to them as they will bring a lot of heat back into the motor.The only thing I don't like about closed cooling is that it clutters up the look of a nice looking engine with hoses and heat exchanger.