My 1995 20hp, model J20CRLEOR, runs well and smooth enough at idle, slow, and at full throttle. When I am speeding up from slow to WOT, I get very rough running and vibration at mid-throttle. I can only describe the condition as ?missing? or misfiring of one cylinder. I still have expected power, so I can not be positive about a misfire, but motor shakes and vibrates terribly.
Sometimes I need to run at mid-throttle, such as when inside a speed zone leaving the launch area. When it starts to ?miss?, I can either back-off or advance the throttle, and it goes away immediately. I would like to have it run well all the throttle settings. Ideas or comments?
Background:
Manual till, rope start, tiller. Three pulls to start cold, half-pull start when warmed up. I just had it serviced, $400, my instructions: ?get it running smoother, oh, and here is the carb kit I was going to replace myself.? The shop found and replaced a leaking fuel connector, and replaced the carb parts. They did not find the rough running mid-throttle.
I have checked compression, fuel flow tank to pump, spark plug wires, and both new spark plugs foul equally. I use fresh premium fuel, proper oil mix, and water pump telltale works. Two SeaFoam decarb sessions, as per iBoats forum instructions, helped a bit with idle and WOT. I can?t think of anything that would effect mid-throttle, but not idle and WOT.
Sometimes I need to run at mid-throttle, such as when inside a speed zone leaving the launch area. When it starts to ?miss?, I can either back-off or advance the throttle, and it goes away immediately. I would like to have it run well all the throttle settings. Ideas or comments?
Background:
Manual till, rope start, tiller. Three pulls to start cold, half-pull start when warmed up. I just had it serviced, $400, my instructions: ?get it running smoother, oh, and here is the carb kit I was going to replace myself.? The shop found and replaced a leaking fuel connector, and replaced the carb parts. They did not find the rough running mid-throttle.
I have checked compression, fuel flow tank to pump, spark plug wires, and both new spark plugs foul equally. I use fresh premium fuel, proper oil mix, and water pump telltale works. Two SeaFoam decarb sessions, as per iBoats forum instructions, helped a bit with idle and WOT. I can?t think of anything that would effect mid-throttle, but not idle and WOT.