installed in old style mudboat with trans and shaft thru bottom. Runs rough and backfires only at 2000 rpm, runs fine at idle and full throttle. Any ideas?

Did you change out your plugs yet that might be the problem.

yes using NGK, batt was not recharging recently and changed the stator after finding the magnets had come off the flywheel. Parts supplier said that is not uncommon for this motor. We also have 2 boat with same engine with other runs fine. Swapped the carb, igniton module and no effect. The other boat also ran same with my parts. I'm wondering if a coil w with plug wire may be bad. Not sure how to check. Trying to confirm problen before just changing parts but it may be my next step..get 2 new coils w wires...thoughts?

hey i had a 25 kohler in my mud boat and had the same problem and changed the cyl. 2 coil and it solved my problem!!!!!