1983 Johnson 175hp idle issue

[bleedblue94]

1983 johnson 175 idle issue

New to me. I've had it for about 3 months and since I've had it I have had a consistent issue at idle. At first I suspected a lean sneeze, so I took the carbs apart and rebuilt them all, replaced all the recirculation valves which were all bad, and upgraded the fuel lines. Runs very well but at idle it misses and eventually dies out. ever so often the motor will bog when i punch it coming out of the hole. if it does so i simply back off it and then hit the throttle again and the motor will take off. at WOT it runs well and pushes the boat at 40mph. at times i do think i hear a very sporadic miss when above idle, but im not sure if its just my ears playing tricks on me

after cleaning the carbs and replacing both fuel pumps and upgrading all lines the motor still has a miss, but it does not seem to sneeze the way it use to. i think it may be more of an ignition miss. one reason im leaning this way is the motor does not level out when the choke/fuel solenoid is used, instead it dies out (I'm assuming the motor is drowning out on fuel). if the condition that is causing my issue were a lean condition, i would suspect that using the choke/fuel solenoid would help the condition by adding more fuel to level the lean condition. bc it drowns the motor out i am leaning towards a timing or ignition issue. any help would be appreciated.

i removed all the plug wires and found almost all twelve of the end connectors were covered in rust. i cleaned each one and removed the rust just to see if it would help and it almost seemed the motor ran worse. ha. i know that these will have to be replaced soon, but they did not seem to be the cause of the issue i described above. i do have a spark gap tool and plan to test the spark soon. all plugs appear to be firing as none are wet, however they all have some amount of oil deposits on them (i use gap-less plugs); i do mix at 50:1 ratio. im beginning to wonder if this is a link and sync issue, but do not have any information on the proper procedure for this motor. perhaps i am going the wrong direction but can someone give some advice and/or provide the sync procedure for THIS motor. thanks

J175txctd

Thanks

 

[bleedblue94]

i think this is an ignition miss and i have one or two cylinders playing around with me with an isolated miss

im thinking tomorrow i will run the motor and rotate disconnecting one cylinder at a time and see if the miss disappears. atleast if i can isolate it in this way i will have an idea where the issue is. i think most likely its a damaged plug wire or a shorting coil

 

[bleedblue94]

well i think the issue is fixed. i tested the ignition system and most all of it checked out. i have already ordered new wires, and i may swap out the coils this winter since some of the resistance numbers were dipping just below the ranges set in the shop manual, but as the issue continued i looked at the synchronization linkage for the carbs and it just did not look right.

when i removed the carbs to clean them i noticed they did look as if they had been cleaned recently, and sure enough the previous owner had probably removed the carbs for cleaning, but when hey reassembled the synchronization linkage he installed it wrong. he mounted it onto the main plate that is directly attached to the throttle butterfly shaft, and not to the adjustable plates. the bar was actually mounted on the outer side of the plates and not the inner side, so all the carbs must have been out of sync. i overlooked this when i rebuilt the carbs myself bc i was so anxious to see if the rebuild fixed the problem. i only realized this was the problem when i took the synchronization bar off and started the motor. it just purrrrrred. it is a pain to synchronize them with the screws to tighten the plates together, but thankfully this looks to be figured out. i should have it at the lake next weekend if not sooner so i will know for sure then.