surge rating?

Hi all,
I'm hoping to get an idea of the surge rating of my well pump that I might know which inverter to get in which to run it off of.
I live off grid, and up to this point, i have been using a briggs elite genny 5550w (8500 surge) 20a breaker, to power it. It would ever so slightly bog down momentarily, so my thinking Is that it was somewhat over the 5k mark. Here's what's known about the pump:
80's (or so the guy whom I bought it for told me) goulds submersible 110v 2 wire, 1/3 hp franklin motor. 8.9 amp rating. Model Number illegible, so the folks at goulds were of no help. I had a kilowatt hooked up and recorded a 900-1100 running wattage, but the surge was too fast to track.
The pump is in a shallow well with a total lift off less than 20', horizontal draw around 150'.
The pump feeds a wellxtrol 80 gal pressure tank and typically runs 2-3 minutes a day.
Here's my questions:
1) any informed guesses as to the surge?
2) is it critical the source be true sine wave?

I'd rather not pony up the 2k that an outback 3524 would set me back just to run a pump, but I'm wondering if a samlex 3000w sa (6k surge) would do the trick as it's substantially cheaper, and pst to boot. For what is worth, my bank is 24v, 225 ah.
Any insight from the resident pump gurus would be greatly appreciated. Though i could get another genny, my plan was to get an inverter eventuality to do the job anyway.

Starting amps of a submersible are about 6 times the running amps. In the motor specification sheet this would be the same as Locked Rotor Amps. You can reduce this by 20% if you use 160’ of #12 wire. This works like a resistor and limits the starting current of the motor, similar to a soft start. Also starting the pump against a closed or almost closed valve will greatly reduce the starting load. Using the longest length of the smallest possible wire and starting the pump against an almost closed valve will greatly reduce the starting load.

It is hard to soft start a submersible. The motor needs to get up to speed in about 1 second to prevent dry running of the thrust bearing. True sine wave is best, but any inverter will create voltage spikes several times the normal voltage. But it is only a 1/3 HP motor, so it is not that big of a deal if it doesn’t last long.