I am not losing coolant from the closed cooling system and yes I went back with the stock 496 exhaust I even pressure tested it before I put it on so I guess my next step is pull the cooler and pressure test it.

Only thing left if all else is known good. You could have residual water in it from a previous issue that has not steamed away yet.

Regardless, change the oil and run it up to temp for long as possible and watch it. Run it with oil fill cap off.

Ok I have pressure tested both closed cooling systems and found a small leak on one heat exchanger I had it fixed and pressure tested both engines over night and both never lost pressure or any fluid. I also pressure tested both oil coolers with them out of the boat over night on full water hose pressure with no leaks is there some way that the water could of came through a pcv valve or the oil fill tube when I washed the engines before I put them back in the boat?

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