Make sure you check the anti-siphon vavle. Mine used to suck water after the engine was turned off. While they "cool" , if the anti siphon valve is stuck it will suck water back into the engine though an open exhust valve. Mine did it so often until I figured out the cause, I used to open the four bolts on the transmission cover and suck the oil out with a bigger
pump rather than though the dip stick tube. It was on a Catalina 30.