i have 500hp that have are fresh, i have installed crossovers w/bypasses and thermo. i have to much water temp--goes to 210 at idle but as soon as you are on plane, drops to 150 degrees. oil temp stays at 190-200 while running, should i drill holes in therm, or restrictors, or am i missing somthing?

What t-stat temps you running? And yes drill them. or they will never regulate properly. Start with two small holes (1/8 inch) on opposing sides. I do not know the temp of the water you are running in. So start small and you can always drill bigger. I run in 50 to 60 degree water with 160 t-stats two 1/8 inch holes and 130 to 140 degree engine temp. Same engine set up.

not sure what you have going on but I run the sane engine, with a crossover, w/by pass and a 140 merc therm, runs about 150 all the time....Rob

Drill 2 1/8 holes in the thermostat on the edges. I run a 160 degree therm and the temp at idle HOT is about 170, running is 150. Hope that helps.

i am running 160 degree therms and water temp is 65-70 degrees, still should i drill holes, it seems like there is a lot of water at idle, more than with circ pumps

That is what I was told to do and it works. It relieves water pressure and keeps more consistant temps.

I am with jeffsway. Drill the two holes and it will help regulate the temps. There is more water at a idle. When at WOT and trimmed you loose pick up ability, depending on the drives (assuming B-1's) and pickup location. I trim and watch water pressure, as soon as the boat gets loose you can watch the water pressure drop on mine. Put the drives back in a little and wp comes back up. Good Luck

2 1/8 inch holes is the answer. With one 1/8 hole my running temp would fluctuate so much at times that it would activate my high temperature warning alarm. When I tried the smallest restrictor in a set of three from Jegs, I could not achieve and maintain a desired engine temp.