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1986 Johnson 90HP

S

Skandicsalad

New member
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1986 Johnson 90HP
Model: CJ90TLCDC
Serial: C 8214105
Spark plug QL77JC4 x4


Hi folks,


new to the forum. I recently picked up a beauty 18’ with a 1986 johnson 90hp (model J90TLCDC). The guy i bought it from said that it has been parked for 3 years because he was working out of town. It ran perfectly before he parked it but not anymore. The guy is a friend of a friend so I dont believe there is any bs to the story.


I tested the coils and spark plug boot/wire with a multimeter, tested all cylinders compression, changed all spark plugs, verified plugs were sparking, fresh gas, cleaned the carbs. Fuel pump has fuel coming out of the outlet when i crank. It starts but runs very eratically and has a real nasty backfire sound very often. It also shuts off abruptly for no reason (no bogging down). Plugs were quite black after trying to start it/get it to stay running.


I just noticed last night that the 2 holes in the back of the motor right under the powerhead (i believe they are for water and exhaust to come out) had a plastic plug in each of them. Previous owner had no idea they were there so he must have brought them to a shop to get it serviced or stored for the winter. They must have put the plugs in while they were doing some work on it or just for storage to keep the critters out?


These 2 Holes have been plugged with the plastic caps the whole time I was trying to get it started/letting it run on the muffs. I hope this didnt screw anything up because of this? I also noticed that the bottom of the left cylinder head is covered in black fuel almost looks like its been coming out of the head? Also lots of black was coming out of those plugged exhaust holes


anyways, it still doesnt run good (backfires a ton). Any other ideas what might be going on?


thanks in advance.



 
Those compression values ( if tester is good ) are a bit low.-------Plugs spark , but does spark jump a gap of 7/16" on a testing device ?
 
I was running it for quite a while on the muffs before i realised that the 2 exhaust ports on the back (just below the powerhead were plugged with plastic caps. Does that mean water was getting in the engine? I dont really understand what those 2 holes do as most of the exhaust comes out the prop? Any thoughts as to possible damage caused by running it with them plugged? Engine was puking black stuff all over the place after running it with the holes plugged
 
Built in fuel tank? Sitting for 3 years I would go through the entire fuel system before you do anything else. Order carb kits.
 
Not a built in tank. Runs on cruise a day. Lots of fuel comes out motor end when i squeeze the ball. Fuel pumps are pushing out lots of fuel when i took the line to the carb off and cranked. Also took the carbs apart and gave them a good cleaning. They were quite clean to begin with. I dont notice any sort of fuel filter. I guess i will try to jam an inline filter in there somewhere? I dont want to rebuild carbs because there didnt seem to be any need when i had them apart. But im at my wits end so maybe I will get a carb kit.
 
The plugs seemed to be wet when i checked em after running. So i didnt think fuel supply was an issue. I thought i read somewhere that you can get water in your engine if the 2 exhaust/water releif holes on the back top of the shaft are plugged. That made me think maybe it was water i was seieng in the plugs? Engine wouldnt run if plugs were soaked though? I dont know. Anyone have any info on the 2 holes on back/effects of running when there plugged?
 
I can not see, hear or feel your motor.----Is it running with VRO oil injection in service ?-----Regular fuel pump mounted in the proper place on intake manifold ?-----Running on 50:1 mix ?----Inspected flywheel key ?-----You might want to remove bypass covers on side of block , 4 covers with 6 bolts 1/4" each.----Let you inspect pistons and rings.---And does spark jump a gap of 7/16" gap.---Are the high speed jets ( orifice plugs ) confirmed clean ?-----Up to you to do the inspection and post the facts.
 
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