I have a pair of 502 carbed raw water cooled motors in the 430 hp range. They run the same except the port motor's oil temp guage doesnt move for about 20 minutes of idel, then it starts to work and matches the motor's oil temp up to 220 and back down when cooling.

I suspect one oil cooler has a bypass/thermostat and the other doesnt.

I boat in Florida 80-degree water year round and have a 20 minute idle ride to the nearest speed zone. Do I need the bypass or not? I'd like to them behave the same.