ORIGINAL: pimmnz
RPM isn't the problem, it only runs hot if there is either no air over the fins, or no oil in the fuel, ie too lean. Consider that about half the cooling is done by the air, the other by the oil in the fuel...
Evan, WB #12.
I beg to differ. If you run too small a prop it wil overheat. A 13X4 must have had it running 14,000 to 15,000 RPM Way too fast for an FX 91