Hi Norm,
it's hard to guess how much more power I need.
This engine was a donor from my next door neighbour (Jims Mowing franchise).
It starts first time everytime and does not blow smoke. I am unsure of how many hours this engine has done but guess being commercially used it would be heaps.It might just be too tired to make enough power.
You are correct in saying it only drives the alternator and blades however , the alternator then makes power for the drive motors and our property is very steep.

Might have to look at a larger capacity engine to suit my application.