No matter what I do, I can by no means get this boat to pump in seawater for cooling. I even insert a port into the loop to see if the hull will flood to demonstrate that water is flowing, and it doesn't. I've checked this setup over and over again, have tried both the small impeller and the modular engine pump. Have tried submerging the pump to ensure it's not full of air or failing to prime. Absolutely nothing pulls in seawater. I guess I will have to use radiators.