im having the same trouble getting the engine warm with a carborated hp 500 with a intercooled pro charger m1sc.im in CT and the water is still in the 40s and i want to take the boat out soon.in the directions for the pro charger it says dont run a thermostat.but running it with the garden hose this weekend for 20+ mintutes dosnt even move the water or oil temp without a t stat.i called procharger and they said i can run one if i drill a couple 1/8 inch holes in it.but after reading this post it looks like it might make to much water pressure with a t stat installed?.not sure what to do.i dont a have water pressure gauge and really dont feel like hooking one up.the boat is a 29 krytonite and should go 90+ and has a low water pickup so im sure it already has a lot of water pressure without it be held back by the t stat