The raw water pump impeller is in the out drive. It has a water pump and thermostat on the motor set up just like a car, since I am running dry headers the water is dumped thru a fitting on the back of the boat.mine's taken off the crossover, need to be more specific as to what your running for
a cooling system tho.....bulb
thats about all an alpha impeller can produce anyways. The motors and gaskets will handle the pressure. Watch the video of the DCB going 170. the pressure spikes MAX the gauges.I think 35 psi might be double what you should seek for an avg sbc or bbc. If you run an mls gasket you can get away with more. 15psi is probably adequate.
Thats why I installed one in my Eliminator. Several years ago took the boat to Tahoe when the lake was fairly low, and the Keys were inundated with hydrilla. Outdrive must have been in a patch of that crap when I first started the engine. Plugged the water intake and smoked the raw water impeller. On my stock HP500EFI I see around 5lbs at idle, and in the 13-15 range at cruise rpm.I am a big believer in water pressure gauges. Especially if you boat in areas that have a lot of sand or debris. It is a great indicator of a plugged water intake or impeller wear.
thats wt mine runs20-30psi,+/-5psi is good. You can install a pressure dump if it get much higher than that.