Here you go, a good used steam enginehttp://www.enginads.com/classifieds/sho ... 5654/cat/7
By the way, this engine requires 150 psi steam (366 deg. F. saturated temp). Sorry, an Axeman-anderson won't work. You might use the AA to preheat the makeup water required.
A simple steam engine will require about 45 lb/hr per hp of steam. That would be 360 lbs an hour for 8 hp. 150 psi steam would require about 1197 btu/lb to produce. At 75% combustion efficiency, this would only be a 576,000 btu input high pressure asme boiler. Finding a coal boiler this small would be hard. Hurst makes small coal fired high pressure boiler starting at 2,000,000 btu's. You could run more than one steam engine with that.
See this web page:http://www.hurstboiler.com/boilers/soli ... ser_hpd_uf
I imagine they could set you up for around $100,000.00.
Sorry for the tounge in cheek reply. Please don't be offended. I applaud your interest, but you will need to learn alot about steam and thermodynamics before understanding why this won't work. The old open cycle piston steam engines were as little as 4% efficient from the coal fire btu content to the work content. Even todays modern extreme high pressure steam powered turbine generators have a maximum thermodyamic efficiency in the 34% range.