1999 Johnson 90hp J90PLEE (Missing)

[Gary Mac]

Hello All

Have a 1999 Johnson 90hp J90PLEE. Which is missing some times. Does not like 3000 rpm. Sounds like it is dropping a cylinder but problem is intermittent and is worse at some rpms. Particularly noticeable at 3000 rpm. Have tried changing plugs and used SeaForm in the gas. Changed fuel filter which is under the air cleaner. Boat is a pontoon boat and has oil injection system. Can someone give me what the correct timing is for this outboard and what is an exceptable range for a compression check. Any ideas would be appreciated.

Thanks
Gary Mac

 

[multimech]

Re: 1999 Johnson 90hp J90PLEE (Missing)

It is an optical ignition engine. I would suspect the eye and "power pack". Seafoam won't clean carbs, make sure they are clean and free of obstructions. Make sure the entire fuel system is clean. The compression will be correct if it is high (90-125 depending on your guage) and even (meaning no more than 10 pounds difference between cylinders). Timing is 20 degrees before top dead center at W.O.T. The idle timing between 2 and 4 degrees after T.D.C. Make sure the plates all open and are in synch. Get back to us on the compression, spark check and seeing each cylinder fire, under load, at problematic speed.

 

[Gary Mac]

Re: 1999 Johnson 90hp J90PLEE (Missing)

Update - did some more testing over the weekend. It appears that the upper two cylinders are firing erratic. Removed both ignition coils, cleaned. Did not spot any corrosion. Took out for test ride. Still having Problems, worse @ 3000 to 4000 rpm. Also seems to get worse on longer runs at listed rpms. Ordering ignition coils mainly because cheaper, if that doesn't solve problem will order module. Hopefully will get a chance to test next weekend.
Thanks
Gary Mac