aTX427

My newly rebuilt HP500EFI is running quite a bit hotter than my older engine. 200*-225* vs 140*-150* at WOT, 180-190 vs 130*-140* at 4,000 rpm cruise. Oil pressure is also about 10lbs lower after a hard pull.

I had it bored to dia 4.5 valve job and blue printed the bottom end. Other than that, the only difference is that I still have straight weight Castrol 40 break in oil vs. 15-50 Mobile 1.

PatriYacht

First things I would do are replce the impeller and the thermostat. Both are cheap and easy to get at. Don't run that engine hard until you figure out what's wrong. I'd hate to see a ruined engine.

hillbilly24

what he siad and also check all teh water hose routing just to make sure it was put back together right, 220-225 is WAY to hot and won't last long at all that way. Don't run it any more until you figure it out.

KAAMA

I agree with Patriot as well, and would do that first. I would also buy a laser temperature pointer gun---just point, and shoot and it will give you a digital read-out of the temperature. They take a TON of guess work out of finding hot spots, and can/will quickly pin point you to where the problem is. I bought one because I was getting a hot reading on my water temp gauge on one of my engines, these were new temp gauges, and sending units, changed the impeller and tested the thermostat and it still showed warm so, I bought the laser temp gun and took my hatch off the boat, and ran the boat as normal, and began taking temp readings from all the water hoses, thermostat housing, etc as my friend drove the boat. Turns out everything was normal---but it was the Levorsi/Gaffrig (spelling?) water temp gauge that was giving false readings and I was using THEIR gauge with THEIR temp sending unit, and it was all new!

You may not need one, but a laser temp gun usually costs about $100-150 or so. However, it you can afford the expense it's definately a nice tool to have on board.