Hard to know why it boiled over after running

Do you smell exhaust in the radiator? Did you retorque the head after running an hour or so? You might retorque if you haven"t. And remove the water down to the radiator core. And not a cup more or you will just complicate matters because she will spit out any excess and you will imagine it"s "boiling over."

So retorque the head, get the coolant level correct, make sure you release the brakes, and see what happens next time.

I will follow your advice, once I get her running again, thanks.

Check the belt tension. 1/2" movement half way between the crank pulley and generator. Put both hands on the genny pulley and try to turn it. It shouldn"t slip.

Sounds like you aren"t moving air across the radiator when it"s sitting still.

Maybe it"s a thermostat problem but I don"t know that it could be.

I'm curious if you can see water circulation or movement in the radiator prior to the boil over incidents, indicating a functioning water pump and thermostat.
I'm thinking that maybe if its a water pump/thermostat issue, when the water in the block gets real good and hot, its popping the thermostat and dumping real hot water into the radiator, where it quickly forms steam- resulting in boil over. Just a thought.