Thread: 350 will not rev when hot

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150 degrees is not a good "normal operating temperature". far to cool. Does it not have a thermostat at the intake manifold? You could be creating condensation in the basepan.
As far as the stalling, I think the voltage jumping around is telling you the story. Put a voltmeter onto the + side of the coil, run the engine until it begins reacting, see what the voltage is at the coil.

It does have a thermostat. In a boat they tend to run cooler a lot with 140 degree tstat. Are you thinking bad alternator?