i have no codes, scanner #'s look good, the IAC was tested ok, swapped it out anyway and still low idle, engine runs smooth but at such a low idle a slight stumble can be heard from the exhaust. the engine has 41, yes 41 hours on it. the boat was in storage for many years, put back in service 2 years ago and ran great, its just now that this issue has come up. cap/rotor clean.