See if you can find a 220 volt 3 hp electric, that will have 4 times the power as the hot tub motor.
Lots of the wood spliters have a 2 stage hydraulic pump and when the splitting gets tough like on some old twisted up Elm, the pump kicks down and that takes power to keep it pushing.
Also like your idea cause sometimes I have done splitting in an open shed, and the exhaust from a 5 hp gas coming back at you is not a good thing. Even being outside if the wind is not right, you are catching wiffs of that exhaust. Not Good.