First time post, i did a search on overheating under sundowners and not sure i found a good match to my experience. I have had two experiences where my temperature gauge pegged to 240. First time it happened was when i was traveling down the river creating no wake, it started to rise in temp, not quite 240 and then plumes of smoke came out of the outboard drive. shut it down, and after about 15 minutes or so, started it up again, traveled at a higher rate, minimum wake, and it never happened again. However, after taking it back to dock, i checked the impeller and found it to be in great condition. I keep it in the river, and someone said it might be some of the river gunk and that i should run it in reverse and forward a few times to clear it out. Then two weeks later, i took it out to the bay and beached it at the sandbar. It was really wavey and the boat rocked a few times and did hit the sand bar two times and the water was full of sand. We decided to leave after an hour or so for calmer waters. the boat started up, and after we raised the anchor, i tried to give it more throttle to get out the waves and away from the sandbar, trim was up...noticed the temp was pegged at 240...give it a bit more throttle and it then just shutdown on me. i lifted the engine cover and smelled burnt rubber or plastic, couldn't tell at that time and some plume of smoke came up. Engine wouldn't restart, it would crank but the pulleys wouldn't turn. I had my friend tow us back in to the mouth of the bay, about a 20 minute tow ride. during the tow ride, i checked all the wiring for any burn marks (plastic smell) nothing, engine did not feel like it was overheating, felt like a normal running engine temp. I checked the belts, nothing out of the ordinary, but i did notice in the engine compartment some rubber shavings on the port side, quite a bit, but we noticed that when checking the impeller the first time, nothing new. Ran my finger over the belts and some rubber dust was on my finger but not a ton. Once we got to the channel, we tried to start the boat again. it cranked, pulleys turned not even a full turn, maybe a 1/4. Tried 2 more times, each time a little more turns until it started back up again. Temp was fine, then i ran it maybe 50 yards with 1/2 throttled....and then drove it down the river for 45 minutes, no wake and wake zones, and it the temp gauge remained at normal operating level 145ish.
So with the impeller in good shape. Any thoughts what else could be the cause of this? Thermostat not opening at certain points? Water pump going bad?
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