Half of my engine is running at 190-210 and the other half is between 130-155? I'm running an eddie marine crossover and the side that is opposite to the water inlet is running cooler the side the inlet is on is running hot. Is this do to the fact that the water has better flow to the right side of the engine or is there something else I should be looking at? I don't want to run the engine until I have this solved...

I'm running the same crossover no issues, seems block is clogged....seen them full of silt or corrosion

I'm guessing its full of silt! The block has just been redone and the engine only has 30 hours on a complete rebuild. I'll try to flush today and see if the problem goes away.

Is it that at idle or cruising? There's often not enough flow at idle to cool both sides evenly but it will balance out as soon as there's pressure.

Its at any speed... It seems to get worse as the engine works harder and its will fluxuate at speed. The opposite side runs nice and cool all the time.

Do you have the same head gaskets on both sides?

Sure do, I just replaced two pistons in the engine do to a lean carb issue. The engine has about 1 hour on it since the reassembly and I know it went back together correctly. I think there may be silt in that side... Any suggestions on how best to flush it?

You could pull the drain plug on that side and try backflushing through the t-stat housing.

I just did a reverse flush and there wasn't any sand or silt but I had high pressure out the drain hole? I blocked off the return on the other side so all the water would have to come out of the "hot" side.... Any other suggestions?

I had terrible problems when I went to crossovers. #8 exhaust valve kept seizing up and hitting piston. 3 corners of the heads would run 170F, back of head at #8 cylinder would get to 250-270F. JimV had me drill out back if my intakes to propagate flow to the back cylinders. I now run 170F all around around after running hard. And 140F idling. Crossovers are sometimes a craps shoot. Other engine no problems, go figure.