I find a spray bottle of water is an excellent way to find a nonfiring
cylinder. Run it a low rpm for a few minutes and then spray a little water
on the exhaust as close to each cylinder as you can. If one does not turn
to steam as quickly as the other then you have found the problem cyclinder.
If it has two carbs that would be the first place I look. A lot of carbs
have a low speed circuit. Sometimes two cylinder engines also have
independent ignition too.

"dragonfly" wrote in message
u...
Hi all,

Just recently bought a little runabout with a 1999 15 Johnson. It seems
to feel like its missing at low speeds but runs fine at higher speeds.
I'm not experienced with boat engines, but I am with cars and it sounds /
feels like its trying to fire but not quiet. The plugs (x2) look ok and
not fouled.

Any suggestions on where to look first?

Thanks in advance for your help