hillbillync
New member
This is my 1st post here and it's a biggie. I've done a lot of reading on this board and have found much knowledge and information. Thanks to all for providing this resource.
My motor started idling rough at the end of duck season this past January. I use it a couple times a week all thru the winter months so it's never sat up which I know can be a source of problems. Also, the problem would usually occur after a prolonged ride and show itself when I slowed down to idle thru shallows or to load the boat on the trailer. There is no indication that I have a high speed / rpm issue. And very recently the problem is becoming less intermittent and more constant even showing itself while running the motor on the hose and muffs in the yard.
Before doing any "real" work to the motor, I replaced the plugs, the internal gas filter, the external fuel/water separator filter, most of the fuel line and the primer bulb. I also performed a Seafoam decarb using the procedure found on this site. All of this did not resolve the rough idle. I'm not a mechanic so I waited until a mechanically inclined friend of mine was available to help.
The first test he performed was removing the plug wires one at a time while the motor was idling roughly on the muffs. On 3 of the plugs a very noticeable miss was noticed when the plug wire was pulled but on one it made much less difference. Also, when the other plug wires were put back on the 3 cylinders a noticeable increase in rpm occurred. When the plug wire was put back on the one cylinder it revved some but not as much. The "weaker" cylinder is the upper right (top starboard) cylinder when looking at the motor from behind. This is cylinder #1 as best we can tell. All 4 plugs looked similar, dark but not overly oily with no carbon build up. The spark gap on that cylinder was the same as the other. Next we swapped plugs and plug wires between the weak cylinder and one of the others but had the same results. Then we swapped the coil packs to no avail. Last thing did that day was play with the idle screws, turning them
gently into the seats and backing them out the same which was 6 turns. This is what they were all set at from the factory.
The next morning, we checked the compression on all 4 cylinders and found them all around 125 psi. My friend decided to pull the carbs off next, all four of them since we were going thru the trouble. All four looked to be in great shape with no trash, gunk, sludge, etc. When they were put back on, he switched the carb on the weak cylinder and one of the strong cylinders, and again, the same results with #1 cylinder being weaker than the rest. Once again relying on great info from this forum, I read to shoot a pre-mix gas mist into each cylinder using a spray bottle. #1 cylinder responded less than the others.
Any ideas on what to do next? My only other thought was the power pack. I read on a post where someone thought that the optical ignition system on this generation of motors was prone to act up at low rpms when an SCR was failing. A new OMC / Bombardier power pack can cost upwards of $300, that's a big chunk of change to put out without knowing it will fix the issue. All advice on a test I missed or if the power pack sounds like the best thing to do next will be appreciated. Sorry about the overly long post but I tried to include all the relevant info. Thanks in advance for your help!
My motor started idling rough at the end of duck season this past January. I use it a couple times a week all thru the winter months so it's never sat up which I know can be a source of problems. Also, the problem would usually occur after a prolonged ride and show itself when I slowed down to idle thru shallows or to load the boat on the trailer. There is no indication that I have a high speed / rpm issue. And very recently the problem is becoming less intermittent and more constant even showing itself while running the motor on the hose and muffs in the yard.
Before doing any "real" work to the motor, I replaced the plugs, the internal gas filter, the external fuel/water separator filter, most of the fuel line and the primer bulb. I also performed a Seafoam decarb using the procedure found on this site. All of this did not resolve the rough idle. I'm not a mechanic so I waited until a mechanically inclined friend of mine was available to help.
The first test he performed was removing the plug wires one at a time while the motor was idling roughly on the muffs. On 3 of the plugs a very noticeable miss was noticed when the plug wire was pulled but on one it made much less difference. Also, when the other plug wires were put back on the 3 cylinders a noticeable increase in rpm occurred. When the plug wire was put back on the one cylinder it revved some but not as much. The "weaker" cylinder is the upper right (top starboard) cylinder when looking at the motor from behind. This is cylinder #1 as best we can tell. All 4 plugs looked similar, dark but not overly oily with no carbon build up. The spark gap on that cylinder was the same as the other. Next we swapped plugs and plug wires between the weak cylinder and one of the others but had the same results. Then we swapped the coil packs to no avail. Last thing did that day was play with the idle screws, turning them
gently into the seats and backing them out the same which was 6 turns. This is what they were all set at from the factory.
The next morning, we checked the compression on all 4 cylinders and found them all around 125 psi. My friend decided to pull the carbs off next, all four of them since we were going thru the trouble. All four looked to be in great shape with no trash, gunk, sludge, etc. When they were put back on, he switched the carb on the weak cylinder and one of the strong cylinders, and again, the same results with #1 cylinder being weaker than the rest. Once again relying on great info from this forum, I read to shoot a pre-mix gas mist into each cylinder using a spray bottle. #1 cylinder responded less than the others.
Any ideas on what to do next? My only other thought was the power pack. I read on a post where someone thought that the optical ignition system on this generation of motors was prone to act up at low rpms when an SCR was failing. A new OMC / Bombardier power pack can cost upwards of $300, that's a big chunk of change to put out without knowing it will fix the issue. All advice on a test I missed or if the power pack sounds like the best thing to do next will be appreciated. Sorry about the overly long post but I tried to include all the relevant info. Thanks in advance for your help!
