Thermostat would be stuck open or closed, I wouldn't think it would be intermittent. Is The Water Pick Up clear with no Obstruction? Check the hose that runs from the cylinders to the pee hole. Make sure it's not obstructed.
Thanks for the Heads Up! Our Airport here is Named after 1st. Lt. Paul F. Baer. He flew for the French, Lafayette Flying Corp & The Lafayette Escadrille before we got involved in WWI.
Happened in my early 40's, Severe Vertigo. 3 Doctors later and Thousands of $$$$$$$ in tests, Cupola Othisis. Its an inner ear problem, ENT Doc knew what it was right away. No more problems for 25+ years.
Fin on the Motor should be on the same plane as the Boat bottom. Put motor in the operating position, put a Straight Edge on the Boat Bottom. Adjust the Jack plate to match. Try tilting the Motor to different positions. Use a GPS on a Smartphone for MPH. GOOD LUCK!
Try Rustoleum in Quarts; https://www.rustoleum.com/product-catalog/consumer-brands/stops-rust/protective-enamel. The site has a dealer finder for you area.
Why are you running a 50:1 motor ay 36:1? That along with the 93 Octane fuel won't hardly burn with a match. Try 50:1 with Regular 87 octane and see if that works better. Also 2 Stroke motors don't want to start when it's Cold out!
Make sure NOT to set the Batteries on Concrete! Place them on a piece of lumber. Harbor freight has Float Chargers for around $6.00 with a coupon. I use these on my garden tractor, Motorcycle, boat Batteries, & Jet ski. They work as well as a $30.00 Battery Tender. My original Motorcycle...
Any Home Center re. Lowes can mix Enamel (Oil Base) in any color you want. Much cheaper than Auto Paint. To spray it use Enamel Reducer instead of Paint Thinner. This is what Painters use on Exterior Steel Doors. Hope this helps you out.