Re: which thermostat
DANG! That's a pretty engine. If it wasn't all the way out on the wrong coast, I would have bid on it.
If you don't boat in really hot water, use the 140 degree.
I boat in a river used for cooling electric generation. On a hot summer day, when I pass through the outflow, it is hotter than bathwater. With the regular thermostat, the engine is already a bit hotter and when it picks up the hot outflow water, it overheats-- actually, the alarm goes off. No major problem because it cools right back down when I pass the outflow water stream.
Final thought: When you actually get to run it, let us know how it compares to the 125 performance-wise.