I bought a used stihl 029 super 20 years ago.
Put on a new bar and chain, a new fuel pickup tube and replaced a spring in the clutch.
Run gas with ethanol.
It sits in the shed at my cabin till needed and starts on the second pull and runs great.
I love that saw.
I bought a stihl farm boss for at my house.
Works good but much heavier then the 029 super and not near the power.

I went through this with a pontoon boat last year.
It turned out to be the inline fuse holder by the battery not the actual fuse.
Just cut the old fuse holder out and soldered on a new one and solved the problem.