I have a similar problem...a Yanmar 2GM20
....which starts, runs up to 2,000 rpm
and then idles up and down and when under load, goes down to zero/quits.
I have had fuel
problems. I can't seem to get the fuel line out to take off the line filter in the tank (tank top has limited access to withdraw the top to get at the inlet strainer.
I have read where it might be a timing problem, might be injectors problem and might be restricted fuel line problems (inlet strainer). Fuel filters were cleaned/cleared.
Help...should I just call a mechanic
and be done with it?