weak spark on 86 150 gt

[etex driller]

ok last week had issue with no spark on starboard side on 86 johnson 150 gt was going to swap packs to eliminate that but found plug with black/yellow kill wire had bad plug fixed that problem.did decarb this morning with seafoam deep creep went to lake for wot run jumped right up on plane then bogged down 200yds later thought plugs fouled but they were not got home put on hose and stbd side nearly dies when you pull any one plug wire but port side makes hardly no difference on any plug i know it has some fire cause it bit me and hen boot is almost on plug you see small spark.checked all connections no problem there.lots of experience on iboats so somebody help please whith what to check next thanks in advance.(new plugs,wires,carb kits,100-105 comp. on all cylinders)

 

[etex driller]

Re: weak spark on 86 150 gt

Just thought to add that when I limped back to ramp 1100rpm was all I could get idling in wouldn't take throttle just load up and die and every now and then it would smooth out for a second like it was trying to fire right.also found grey tach wire hooked to grey/yellow wire put where ut goes but can't check it its pouring rain could this be a cause?

 

[etex driller]

Re: weak spark on 86 150 gt

ok stopped raining so went and checked spark and it will jump 7/16" great on all 6 cylinders great put all plugs in fire it up and start pulling plug wires off one at a time and every now and then you could hear very very slight change unlike starboard side which when pulled 1by1would almost kill motor.no arc could be seen in the dark so what could it be i am about ready to smoke again after quitting for 2 months.

 

[emdsapmgr]

Re: weak spark on 86 150 gt

It is easy to see weak or failed spark on a plug wire with an inductive timing light. When you are running on the water and it starts to crap out, get the light out and check each plug wire. You are looking for intermittent or weak flashes. Swap the power packs and see if the running issues change to the other side of the engine.

 

[etex driller]

Re: weak spark on 86 150 gt

Ok I swapped power packs to opposite sides ran to lake and tried to see If stbd side would not fire now but to my disbelief motor gained 400 rpm and 4 mph I don't know what I did but hope it stays fixed I hate these gremlins.

 

[jonesg]

Re: weak spark on 86 150 gt

It could be poor grounds or dirty plug connector pins on the PP.
Maybe clean everything up, apply some dialectric grease to keep moisture out. I use electrical switch cleaner spray from NAPA to make sure all the connectors are good.