I've got to fabricate a cooling system for a 427 ford motor. For reasons I wont go into, it would be easiest to set it up as a preheated (water goes through the exhaust manifold before it enters the block) crossover setup. With the preheat, is a bypass and thermostat necessary.
Water temp that the boat will be running in is 70-80 degrees, and 95% use will be at moderate loads, 2000-3000 rpm.
Gary

if you preheat, you generally do not run a t-stat.

I have a Stainless Marine "pre-heat" set up and it has both a t-stat and a bypass. The t-stat does have 3 small holes (3/16) in it. This way you always have water going to the risers.

Let me know if you need to know how it is plumbed or you can do a search for this topic some time back.

Bob

Thanks for the info guys. I think I'm going to fabricate it for the thermostat and bypass. You can always take it out. I've also heard it's common to have holes drilled in the thermostat with these setups.
Gary