Just got a SailPro to replace my M5B. M5B was still running good, but not great. Anyways…. I’m on break in period now. Since this has a thermostat I don‘t see benefit of using the flush plug. (I’m actually using the plug from my M5B that has hose attached.). Since the thermostat is likely closed it can’t be doing much good. Bucket method is a little bit of pain and muffs are too big to squeeze between prop and water intake. Too bad they don’t make a bag with some kind of port to feed water…