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1984 johnson 90hp

G

Gary Vinzant

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I have a johnson 90hp motor on my skeeter bass boat. To start the # 4 cylinder was not firing which caused a miss of course. The motor had sit a while before I got it so I decided to not only fix the cylinder that was not firing but to do some other things as well. Ok here is what ive done so far... to fix the cylinder miss I replaced the #4 coil first then the power pack for that side. Also cleaned all the electrical connections on the motor with contact cleaner and greased with die electric grease. So now all 4 cylinders are firing. Next I decided to rebuild the carburetors and fuel pump since the motor would flood out while idling at times. Also replaced the fuel line and primer bulb from tank to motor. Ok I got the link and sync and timing out when I did the carbs so ive set the link and sync and timing according to the service manual I have. According to the new timing light I bought today the motor is now in time with the carbs. Also has new plugs and plug wires and a new ignition switch. Fuel filter was also replaced when I rebuilt the fuel pump. Ok now the motor idles great. Idles so smooth you can set a glass of water on it without spilling a drop. Cranks great. As far as the way it runs it runs better now than it has since I got it. Ok the problem that has me scratching my head is the motor wont bring the boat up on plane. According to my gps speed on my fish finder top speed is a wopping 7mph. Before I touched it with a cylinder missing it would plane out build rpms and run about 38mph. Now no plane wont build rpms. It also has a new prop. And I am getting full throttle. By that I mean when I push the throttle handle all the forward then check the carbs they are open all the way. So any ideas where I should check next or what may be wrong? I am stumped so any help would be appreciated. Thanks for any advice.
 
The prop is the same size and pitch. I changed the prop before I did all the work because I hit a stump and bent one of the blades so it would get on plane with the prop before I did all this other stuff. I have not changed the gearoil yet. The guy I got it from said he had just changed it and when I checked it out it looks new. The water pump is working great it peas water good but I could change the impeller because I have bought a water pump kit and have it on the shelf in case I ever needed it. Im assuming the sync is correct. I set it and the timing step by step as it said to in the service manual. Im assuming its correct because before I set the sync it would not hardly idle at all and working die randomly spit and sputter and was very hard to start. When I set sync and timing it ran way better like it should with the exception of it wont plane out. With the engine off in forward gear at WOT the butterflys are wide open and timing advanced to the stop point. Now the carbs opening at the same time ????? Wouldn't setting the sync ensure they open at the same time since the linkage for the 2 are connected? Ill look but I think they are both opening at the same time. I know at WOT the butterflys on both are wide open. Ive been a car mechanic for over 20 years but outboard motors are way way different lol.... thanks
 
Yes ive had it on plane since I hit the stump and I have pulled the flywheel since I hit the stump. I did that trying to run the miss down to clean the magnets on the flywheel because someone told me thats why that one cylinder was missing because the magnets were dirty but they wasnt lol. I checked the compression before I bought the boat to be sure the motor wasnt junk 150lbs on the highest and 140 was the lowest. I also tested the fire on each cylinder with a spark tester when I had the miss on #4 and all are good. The plugs are also all gapped at .40. Thats what the service manual said to gap them. The only thing im not sure about is should the primer bulb stay hard all the time? Sometimes it will feel softer than when I first pump it. I asked the local service guy and he said that should not matter but it seems to me that it would but I don't know?
 
Common misunderstanding that the bulb should stay hard.----------Once motor starts the bulb will go soft and that is just the way it is and normal !!
 
Unfortunately I hadn't had any help and been working on it by myself so I hadn't been able to pump the primer while running it. The plug insulators are not brown instead they are black and I mean black as coal. Ive always run ppremix. Mercury quicksilver 16oz to 5 gallons is what the local service shop told me to mix it at.
As far as the primer bulb it pumps up good and stays hard until the motor starts so I guess thats operating right... not gonna have time to do anything to it today because of drs appt but plan on doing some more things tomorrow like rechecking everything and maybe a temporary gas tank with fresh premix... thanks guys keep the ideas flowing because it does help...
 
The thermostats are in and it seems to be warming up good. I mean its like any other engine it gets to hot to hold your hand on lol but I dont have a temp guage. I was just reading in the service manual about a few things and looking under troubleshooting it talks about clogged reed valves keeping one from building rpms at WOT. Ok so where are the reed valves? Also the primer solenoid seems to operating normally it clicks when I push the key in but how can I check it to be sure its operating normally?
 
Well here is a update so far. I worked on the motor most of the afternoon. I started by rebuilding the starter because it was dragging after it got hot. A set of brushes fixed it so no more starter drag. I took kimcrwbr1's advice and went back and triple checked everything. And as I was I found 2 things. I was pulling the plugs out and noticed that the #1 plug was very loose. So loose I unscrewed it with my fingers. And I also noticed that on the #4 cylinder it would fire thru the spark tester but would not fire thru the plug. So I thought bad plug since its a new coil. I tried another plug and same thing. Long story short after doing other tests I guess I bought a bad coil. So I put a old coil on and hit the key and I can hear a difference in the way it runs. I have not had a chance to lake test it to see if it will get on plane yet. Im hoping this has fixed it. Will report back when I get a chance to test it further. So you guys think a bad coil and a loose plug could keep it from getting on plane?
 
Yes im using a good adjustable spark tester and I noticed today that 3 of the coils would jump would good blue spark but the new coil would jump with a light orange spark and would not fire the plug. I changed that coil and now have blue spark on all 4 cylinders and #4 will fire the plug now. I will never ever buy another CDI coil or CDI ignition part. From now on only oem johnson parts. That was a $45 waste because my local part guy will not take any electronic part back. Said it could be something I done even though I just bolted it on and hooked up the wire but you live and learn. I just hope it gets on plane now when I test it tomorrow if it dont rain that is...
 
I dont think I over tightened it. I always use 1/4 inch drive on electronic parts to be sure I dont break anything. Im not really to worried about it just glad its working now and besides I am still using the new plug wire that came with the cdi coil so I guess I paid $45 bucks for a really good plug wire lol.
 
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