Engine trouble.

[Yurtgirl]

Okay, before we head off to an untried, but recommended mechanic, I thought I'd throw this out to some experienced folks.
Just bought an 86 Tioga arrow from my sister for next to nothing. Before i bought it i helped her drive it from WV to Ohio. it wouldn't do hills and grades well. It went down to 25 mph going up a grade and sputtered a lot. She ended up having it towed home. I drove it from her place to mine and it got up to 55 with no issues and no sputtering but it was flat and only about 3 miles.
Now, other than bad gas, any idea what else might cause it to do this? The beau looked at all fluid levels and they were fine. He said overall the engine looked clean and good. I'm no engine person, so I'm clueless.
Just thought I'd ask.

[CampDaven]

I had a similar vintage class C.

Dump the fuel, fill it up, add Stabil.
Change the fuel filter.
Plugs, wires, rotor and cap for motor.
That should eliminate the usual suspects for making it run.

[OSP1268]

There is a product called "Seafoam" that also will work very well to clean up the gas. You might have to run a couple of tanks through to get everything cleaned up.

[TQ60]

Called a "major time up", plugs, wires, capital, rotor, clean out carb, oil, all filters etc.

Expect a couple hundred in parts, shade tree guy (retired pro who knows what they area doing) can do it all in an afternoon.