Hey,
I have a 20hp 4 stroke merc carb outboard. Engine starts fine...idles smooth forever..well troll at idle forever. Runs strong and smooth wide open. But somewhere between 10 percent throttle 30 percent throttle it runs very rough and sporadic.
Looked at the plugs...top cylinder light and clean...bottom was dark and dirty....changed them still runs same. I was thinking the plug differences was from trolling for long periods and not running it hard enough to clean it up after.
Any thoughts? Perhaps low speed jet is clogged just a hair and won't allow enough when reaching its fuel limit?
I have a 20hp 4 stroke merc carb outboard. Engine starts fine...idles smooth forever..well troll at idle forever. Runs strong and smooth wide open. But somewhere between 10 percent throttle 30 percent throttle it runs very rough and sporadic.
Looked at the plugs...top cylinder light and clean...bottom was dark and dirty....changed them still runs same. I was thinking the plug differences was from trolling for long periods and not running it hard enough to clean it up after.
Any thoughts? Perhaps low speed jet is clogged just a hair and won't allow enough when reaching its fuel limit?