The issue is you actually need to know the torque and rpm requirements for the load. Often gas motors are oversized to provide the torque at lower rpms. An electric motor has close to full torque at zero rpm so often you can reduce the motor size when sizing for the torque curve of an electric motor vs a gas motor but without knowing the load torque curve it is just a guessing game1 hp=746 watts. So 9.9 X 746 = 7.4kw electric motor
Unless it's a diesel engine. But even still, it's slightly oversized to compensate for the spool up to get torqueOften gas motors are oversized to provide the torque at lower rpms.
A gas motor is going to peak at torque somewhere around 1600 -2500 rpm. It will change some based on the compression ratio the higher the compression the higher the peak torque rpm rating. But at 5000 rpm the gas motor will probably have less than half the peak torque.I believe the older 9.9's produce 4000-5000 rpm. While the newer 9.9's produce 5000-6000 rpm.
I keep a separate electric trolling motor when low speed high torque is needed.
Only goal is getting there fast. Top speed