I have what I believe are HP500's in my boat. They use a raw water pump only, with no thermostat.

The engines run way cool, and I am looking into running thermostats this summer to solve the problem.

Did the HP500's come with a circulation pump from the factory? If not, how can I better control the engine coolant temps?

Thanks,

Greg

Yes they do come with a circ pump from the factory. Someone must have removed it to install a crossover. You can install a thermostat, but you must have a bypass for water to flow when the thermostat is closed. Hope this helps.
Eddie

Thanks, Eddie, that does help. I did not know you could run a thermostat with the crossover system. What kind of bypass do I need to run to make sure my exhaust gets plenty of water while the thermostat is closed?

Greg

You will need to run a hose, about 1", from the crossover to the top of the thermostat. You will need a fitting on top of the thermostat so that water can get to the hoses going to the exhaust when the thermostat is closed. They make thermostats with this fitting. If yours doesn't have one, you can either replace it or have a fitting welded on. You will also need the same fitting on the crossover. Again, if it doesn't have one then it can be added or purchase one that already has the fitting.
Here is an example of one type of crossover system that CP Performance carries with the bypass.
http://www.cpperformance.com/detail.aspx?ID=2900
Here is another crossover from Eddie Marine
http://www.eddiemarine.com/store/car...l&p=11554&c=40

Here is the thermostat housing with bypass fitting from Eddie Marine also
http://www.eddiemarine.com/store/car...l&p=11561&c=52

Thanks very much for the info, and for the pics. My thermostat housings are in fact drilled and tapped for fittings up top, but I never knew what they were for.

The crossovers have no bypass fittings on them, but I'll figure something out there.

Thanks again,

Greg

Thanks Eddie, we also have this system which represents one of the cleanest crossover systems available today.

http://www.cpperformance.com/detail.aspx?ID=7588

Good Luck!

is there really a gain from cross over vs circ pump, what about the pulley for your belts. do you just get diffrent belts.

Yes, you do get shorter belts. There is a slight hp gain from removing the pump. Will you see it on the speedo? Doubt it. I don't run a circ pump or thermostat in my engines because I want the engine to run cold. However, the engine is set up to run cold. It allows me to have a more aggressive tune if I want to and not have to worry about detonation.
Eddie

I had the same issue on my boat when I got it, had a crossover with no provision for a bypass, ran way to cold, sold it bought one that did, istalled a std merc therm. works great, one less thing to worry about failing....Rob