For some reason small gas engines are rated at gross HP, and when you
subtract the power used to run the cooling fan...

Not really, we have run these small engines on a legitimate dyno at one
of the major lawnmower mfg facilities. (They paint their stuff red) The
engines tend to put out less than the engine mfg lists: something like
95% of the nameplate number down to not much over 50%

But the real reason you need a larger gas engine than electric is that
the gas engine has no additional torque capability, an electric motor
does. A 20% overload for 1 second will kill a gas engine cold. Same
overload on an electric motor will cause a surge in input power, not
much else.


And find out the optimum speed for the pump head - probably 2,400
RPM to 3,600 RPM range common for gas engines.

I'd expect ANY pump in this class to be set up for 3600 rpm. It's the
standard speed for both gas and electric motors.

This style pump head is meant to direct-mount onto a certain tapered
crankshaft tail normally found on gasoline engines - which you are NOT
going to find on regular electric motors. The pump impeller has the
female of the tapered shaft with the lockbolt, and the tolerances when
it's all bolted together is critical.

The OP listing clearly states "3/4 inch straight shaft with keyway"

Pool pumps and stationary pressure pumps are built to bolt to a
standard C-face pump duty motor with straight keyway shaft, not these.
If you search, you can probably find a semi-trash style pump made for
an electric drive - just like you can find prerssure washer pumps
built both ways.

If you really want to go electric with that particular pump head,
you need a pedestal adapter for the pump.
A lot of work with no benefit.

It has the proper tapered
shaft with center bolt, a pedestal in the middle with two shaft
support bearings and and bolting face at one end to mount the pump, a
mounting foot built into the casting, and the other shaft end has a
straight shaft with keyway to mount a standard drive pulley or a
Lovejoy Coupling.

Thern you vary the pulley ratios to drop the speed a bit from the
3,450 RPM of the electric motor to the ~2,400 RPM that the pump head
really wants.

-- Bruce --