Do you have a gate valve at the pump?
Set it for 140°f at cruise. Its a single pass system, it gains (passes) more heat than a car/closed cooling system.
Lower water temps gain horsepower. It's been proven on the dyno for years.
At 180°f, lake water is precipitating hard water minerals into the water jackets, a recipe for disaster.
I wouldn't run it over 160°f, ever.
Some simple math-
Lake water in @ 70°f, + 70°f heat gain from the engine, 140°f.
A good radiator only cools about 50 degrees. At 210°f output, the radiator will cool it ~50°f, or to 160°f, -ish.
Higher temps in cars are mainly for emission requirements.
If it had open headers, I'd run it at 110°f, at cruise.
Just my $0.02.
Dan'l