Pay up, fill us in some details on your build. I'm doing 2 509's for my own boat this winter (on top of 6 other builds) with bob.

I'd want to know why it was overheating.

UPDATE.................... Spoke to Bob Madera at Marine Kinetics, truly a gentleman and a wealth of information. First step is pull my engines, I am only breaking down the engine that the head gasket blew on, after the magmaflux and the sonic gram of the block and crank. If the block and crank are good, then I will disassemble the other motor take that to the machine shop have the same processes done and start to proceed rebuilding to 509s basically stock short blocks, but then; Aluminum Heads, roller valve train, Marine Kinetics custom grind cam, single plane manifold, Nickerson 950, stainless marine exhaust, etc. should be a 625 hp combination per Bob M.

If the block and crank are bad it will be 2 Dart big M block, with scat rotating assembly for a 598, then whatever Bob M recommends for the heads, valve train etc.

I will then sell the other running 502 complete, to generate revenue for the build.

As far as the overheating is concerned all new oversized oil coolers, oversized lines with sweeping turns, retain water pumps with thermostats

540 with Callies Compstar cranks, Callies Ultra H beam rods, Carrillo pistons, AFR oval port heads, 300cc, full CNC porting, runners and combustion chamber, Victor Jr 4150 flange intake with a Reher-Morrison anti reversion plate and spacer and Pro Systems Dominators. Scorpion Roller Rockers, and Bob's roller cams, and stud girdles. SM exhaust with dry tails. I got them finished and Installed last week in June and have around 250 hours on them. My only regret is not having a faster hull. Looking for that now.