running at slip in idle and after 5 minutes in stalls out. restart and have
to throttle up out of gear around 1100 rpm to keep it going. soon as
I put it in idle it stalls out.

I have replaced both fuel filters, new fuel pump. new distributor/rotor.
last year new spark plugs.

had old gas in it. I added new gas before I ran it to slip... ran fine then.
added seafoam and more gas to it at current location.

back fires to?
sometimes I notice rpms bump up and down a bit when I'm not
doing anything to throttle?

any ideas? 2nd year owning boat.