proteus503
Recruit
- Joined
- Apr 8, 2012
- Messages
- 4
I've been scouring this forum looking for similar issues, and I think that I have the issue narrowed down to spark, but I need some assistance in diagnosing which part to replace.
Working on a friends 25hp johnson. The model and serial numbers are gone (worn off), so I'm trying to ID the motor as well as fix it.
Replaced fuel (borrowed the tank from my own boat, gas is fine)
Pulled carb, cleaned carb and reassembled (flossed jets, checked gaskets, checked float clearance, cleaned float valve, 99% positive that the carb is in good working condition)
The motor starts instantly, cold or hot, literally a "one-pull" motor (if it werent electric start) The issue is that as soon as the motor gets warm (after 10-15 seconds) and you apply a small load (a bit more throttle than idle), the motor will misfire every one or two seconds, and send out a plume of unburnt gas smoke through the exhaust (not a backfire, it is not running lean).
Pulled plugs, checked compression (95psi top cylinder, 100psi bottom cylinder), replaced plugs with new plugs, properly gapped. Heres where it gets interesting. After I replaced the spark plugs, restarted the motor, ran it for a 30 seconds or so, I pulled the plugs back out, and noticed that the bottom cylinder looked fine (normal, dry-soot deposits on plug), and the top cylinder was all oily, which leads me to believe that the plug is fouling and causing the mis-firing.
Swapped the coil packs (bottom to top and vice versa), cleaned plugs, restart motor, recheck plugs, top plug still oily.
swapped plug wires, cleaned plugs, restart motor, recheck plugs, top plug still oily.
So after all of this, I read through some other johnson 25-30hp threads looking for similar issues, and the conclusion that I came to is faulty ground, or faulty power pack. OK, tore apart every electrical connection on the motor and double checked that everything was intact and well grounded, problem persists, so now I'm back to faulty power pack.
Being that I dont know the serial number or model number of the motor, I am unable to find the proper schematic. searched several johnson 25 schematics for mid-80's models on marineengine.com and found something that looked simliar:
http://www.marineengine.com/parts/j...J25ECCM&manufacturer=Johnson§ion=Ignition
part # 20 is the power pack assembly, but I am unable to find that part anywhere on the motor.
It is likely that I have the wrong schematic, so I guess my first request is to ID this motor, and take suggestions on what the problem might be.
Here are some links to photos of the motor:
http://home.comcast.net/~proteus503/pwpimages/IMG_0268.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0269.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0270.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0271.JPG
I sincerely appreciate your time and advice. Thank you, and cheers!
Working on a friends 25hp johnson. The model and serial numbers are gone (worn off), so I'm trying to ID the motor as well as fix it.
Replaced fuel (borrowed the tank from my own boat, gas is fine)
Pulled carb, cleaned carb and reassembled (flossed jets, checked gaskets, checked float clearance, cleaned float valve, 99% positive that the carb is in good working condition)
The motor starts instantly, cold or hot, literally a "one-pull" motor (if it werent electric start) The issue is that as soon as the motor gets warm (after 10-15 seconds) and you apply a small load (a bit more throttle than idle), the motor will misfire every one or two seconds, and send out a plume of unburnt gas smoke through the exhaust (not a backfire, it is not running lean).
Pulled plugs, checked compression (95psi top cylinder, 100psi bottom cylinder), replaced plugs with new plugs, properly gapped. Heres where it gets interesting. After I replaced the spark plugs, restarted the motor, ran it for a 30 seconds or so, I pulled the plugs back out, and noticed that the bottom cylinder looked fine (normal, dry-soot deposits on plug), and the top cylinder was all oily, which leads me to believe that the plug is fouling and causing the mis-firing.
Swapped the coil packs (bottom to top and vice versa), cleaned plugs, restart motor, recheck plugs, top plug still oily.
swapped plug wires, cleaned plugs, restart motor, recheck plugs, top plug still oily.
So after all of this, I read through some other johnson 25-30hp threads looking for similar issues, and the conclusion that I came to is faulty ground, or faulty power pack. OK, tore apart every electrical connection on the motor and double checked that everything was intact and well grounded, problem persists, so now I'm back to faulty power pack.
Being that I dont know the serial number or model number of the motor, I am unable to find the proper schematic. searched several johnson 25 schematics for mid-80's models on marineengine.com and found something that looked simliar:
http://www.marineengine.com/parts/j...J25ECCM&manufacturer=Johnson§ion=Ignition
part # 20 is the power pack assembly, but I am unable to find that part anywhere on the motor.
It is likely that I have the wrong schematic, so I guess my first request is to ID this motor, and take suggestions on what the problem might be.
Here are some links to photos of the motor:
http://home.comcast.net/~proteus503/pwpimages/IMG_0268.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0269.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0270.JPG
http://home.comcast.net/~proteus503/pwpimages/IMG_0271.JPG
I sincerely appreciate your time and advice. Thank you, and cheers!
