Originally Posted by
mimms2
As said, good fuel, clean oil. New and gapped plug.
Also check/gap your magneto, I assume it has one.
Check for vacuum leaks around carb gaskets/boots - squirt a bit of CRC66 at them while it's running: if the motor picks up - you're sucking air and any other tuning is going to be chasing your tail.
Two and one-half turns out is a good starting point for all carb screws. If the carb has an idle-circuit that will probably be it, and you'll tune your top end for best performance/economy wherever you want it (trolling, or travelling?)
I'm gonna have to disagree with VC, 2 toke oil is 2 toke oil. But I'd go for motoX or stihl, rather than budget lawnmower stuff. You mix to the OIL specs not the MOTOR spec (oils have improved a bit in the last century) but you're always better running more than less.
There was a diagnostic method on the old 2T racing bikes called "plug chop" - not sure if I'd do it to an outboard though. Run it at the problem load/revs, then cut the ignition. The condition of the spark plug will tell you what's wrong.