Since your in a huricane hit area suspect bad fuel. I'd isolate your Onan fuel line to a seperate fuel tank (plastic boat fuel tank from Walmart) and run new good fuel. During Hurricane Katrina there was TONS of crap gas floating around. SEAFOAM was a life saver! Vehicle engines may run better on bad gas than Onan engines.
Also confirm that your valves are set correctly and your air intake line is not plugged.
I knew a guy who bought a cheap engine at Harbor Freight and hooked up his hydraulic hoses/adaptors to after bolting it to his bin top. It ran slow, but it ran. It was a Versalift boom.
Good luck!
