I restored my old Fountain it sat a while is it OK to use in fuel tank??

My 2 cents is to drain the tank and put fresh fuel in with some additive.

What is "a while?" and what engines??
If more than 2-3 years, I'd probably drain it.

I have to deal with the same and going to drain the tanks. Just isn’t worth it. If was a pair of 330’s I wouldn’t be as concerned. You can always use the old fuel in lawnmowers, tractors etc.

Btw I’m going to use an old electric fuel pump.

And climate.

Gas loses octane fast in Fla, not so much in Ohio.

Regular gas, not in Fla, 2 yrs old, would scare me.

Smell it.
It stinks when it starts to turn to varnish.

As to Seafoam, I swear by it!
Cars, boats, motorcycles etc.

Its biggest bang is clearing carbon from rings etc, EFI injectors and carbs.

Also in DFI vehicles.

I buy 6 or more cans per.

Close to a year sat in 1 marina when we moved it I filled with hi test? It's a 27-29' Fountain 2x454HO 1990.New guy water tested it a few times and I drove it on a run last Saturday. I hear popping from both motors idle and at 3800=4000 maybe fuel? I hope not springs or valves oil pressure good motors power up fine? Going to fill her up again today and see?? PS the gas does suck in Florida thanks!

If you suspect bad gas, do a sample. Remove a fuel water separator and fill a clear clean dry jar or bottle. Wait 1hr.

Do not refill the boat ! you need to remove the old gas if bad.

My goodness.

btw: cap/rotor /etc can do same thing. Take a look.

Drain it, fresh gas, K100 additive.......................or you will chase fuel related gremlins.

Going to check fuel filters put new ones fill her up and use her?

I suspect your problem is not bad fuel related. JMO…. Regardless follow the advice given or it may haunt you!