Update: I started to feel like I was really at an impass where I couldn't know if there was really something wrong with this motor until I went and opened it up for a while.
So I did that today. It was barely running at first, I had to push the choke button non stop. But eventually it started to run and I was able to give it more and more gas. I suspect I might have left some bad gas in there last season when the original overheating thing happened. Eventually it smoothed out and whenever there were no rowers or kayaks in sight, I would go lets just say, greater than headway speed
Also this was on super fresh fuel with 2oz per gallon of Seafoam.
No overheating issues. No overheating beep, also the one time I opened the housing and felt the motor, this was at low rpm low speed, it didn't feel hot. So I think these two problems are fixed. I guess I'll never know what really fixed the overheating. Was it the impeller, was it the thermostat, was there a piece of seaweed that got jammed in there and after drying out for 12 months, going full throttle blasted it right out? I'll never know but it's real nice to be able to get out on the water again! I wish I had gotten it done 2 months ago but oh well.