Okay, I'm ordering the Seakamp remote mount cooling setup. oceaneastmarine wants to sell me the full system that cools the manifolds too. He says he runs 750HP with the same system with no problems. I originally wanted a half system because I thought cool seawater would be better in the exhaust rather than hot antifreeze.

With a full system, is seawater still going out the exhaust? I'm confused on how much of the exhaust is actually cooled my antifreeze.

What system do I want? I don't really care about my manifolds- I'm going with Stainless marine units next spring.

In a full system the manifold is isolated from the elbow (which is where the overboard discharge is). The manifold gets antifreeze, the seawater is discharged through (and cools) the elbow or tailpipe. In the 1/2 system seawater cools the manifold, then goes to the elbow & out.

As about 1/3 of the heat produced winds up in the exhaust a bigger heat exchanger is required for the full system.