Purchased boat and had a tough time starting and at low idle. Mid range on up it ran like a top. Mechanic said this particular motor has a Sure Start feature...not sure what that is. He also said each cylinder has a thermostat and one was full of sand and junk. Therefore it was loading up on the low end...which made sense. He pulled something off and let the motor run a bit and the water flushed it clean. It then ran great. It's now acting up again. For starters I didn't know each cylinder has a thermostat, but I would like to flush this out myself to avoid the 100 miles round trip and the $85 to do what the mechanic said I could do. I don't even know where the thermostat(s) are on this beast. Anyone help explain how I can go about flushing the thermostat?