1983 175 johnson fouled plugs weak spark

[bleedblue94]

motor has run great lately, but in the last week became very hard to start, would seem to load up on fuel and hesitate on hole shot, and then became almost impossible to idle. now, it is clearly not running on all cylinder at all times. yesterday when it died at the dock i pulled the plugs and all were black and wet. i did not have any fresh ones with me, but i cleaned and dried the ones i had and the motor fired right back up and worked fine. i took it out for a short ride and then when i went to idle again the motor slowly ran worse and worse until it eventually just died out. i do know i am due to rebuild the carbs, and plan to do so this weekend, but the spark appears weak on all 6 cylinders. it is not likely i have 6 coils dying out at the same time, but i would think it is possible to have 2 power packs dying a slow death w a motor this age. i am curious if there is anything else i should immediately check that would have an affect on all six cylinders? poor ground was one thing that came to mind but grounds appear to be clean and healthy.

TIA

 

[Bosunsmate]

Re: 1983 175 johnson fouled plugs weak spark

Check carb inlet valves and floats during rebuild.
Stator failing could cause it, rectifier problem too

 

[bleedblue94]

Re: 1983 175 johnson fouled plugs weak spark

Check carb inlet valves and floats during rebuild.
Stator failing could cause it, rectifier problem too

got a chance to test the ignition system, 3 cylinders passed the 7/16 test, other three were very weak (not all on same bank). i changed out coils with w those from an extra motor i had lying around and they seem to be fine now, but i will test again tomorrow.

when i went to test run the motor i noticed fuel coming out of the airbox. i took the airbox off and ran it again and could see fuel coming out of the bowl vent for the top carb. took the carb apart and the float seems fine so i am assuming the needle and seat are done for. i have three rebuild kits sitting in the garage so it looks like i know what im doing on my friday...

 

[emdsapmgr]

Re: 1983 175 johnson fouled plugs weak spark

A simple ignition test is to swap the two power packs. (one controls the spark to each head.) If the "no spark" problem moves to the other head, you need a new pack. Since you have issues of weak spark on both heads at the same time, the power pack swap won't provide you much new information. Best to check the voltage output on the stator. Possible it's below the minimum required. When the stator outputs low voltage, it won't fire all the plugs on every rpm. It may randomly not fire. Keep in mind that when cold, the engine may run fine. Weak ignition components tend to fail once the engine heats up to normal operating temps. If you don't have a factory service manual, check out the ignition troubleshooting for your engine at: cdielectronics.com I believe the minimum voltage output for your stator is around 200 volts when cranking. (as measured with a special peak-reading voltmeter.) Check that spec.