Jim, you can safely get a 140, the amount of continious work involved is immense, its the untold truth to it.
there is a great deal to do on the run, but like all tools a system forms quickly. having 3 of you digging, processing and prep
would work hands down, if you for what ever reason believe bigger is best, ( goldiggs and i believe this
) then look at a Keene 151.
you wont keep up with it but in terms of processing good material it only helps you to recover more gold in the heaps you speak of.
Hey Digger, to anser the noise and starting a fire thing, mate.........seriously, dont look too far into it, if you prepare your work area to be safe then there is no chance of a fire starting, as GD stated, all machines by laws standard should have the arrestor fitted, and noise, im yet to come across a pump, be it 4 or 2 stroke that is silent. its the nature of the beast, and ear muffs work a treat to combat the noise
so its a personal preference, i like the concept, method and end result.
in saying that, i must go dig