'85 johnson 150 GT loosing spark / weak spark investigation

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
I have been loosing spark on 3 cylinders and have been pulling my hair out trying to find the problem. After $750 on new power packs, coil and VRO (the VRO was upgraded to OMS and was needed) still the same problem.
It all started with a miss at WOT. It was intermittent so it was really hard to pin-point. It then became a problem when putting into forward. The motor would die and wouldn't go above 1200 RPM. I replaced / upgraded the VRO to OMS and checked spark and found a coil that wasn't firing. So I replaced that. The problem was still there though. I did a test on the stator and found nothing wrong. I pulled all my wires and ohm tested everything and still nothing. I was at a loss. I rechecked spark again and found that I not only didn't have spark on the new coil but the other 2 cylinders on that side were barely sparking. I bought a new power pack for that side figuring there was nothing else it could be. I was wrong. Still very low spark on the 3 cylinders on the starter side. I was now really at a loss.
Today I was looking to see if I have a 10amp or 35amp stator so I could replace it and noticed a magnet out of place on the flywheel. It had became loose and slid against the magnet next to it. This will cause the lack of spark on 3 cylinders. I am taking the flywheel off tomorrow and will be JB welding the magnet back into place. All this time and money for something that would be almost free to repair. I hope that by posting this it saves someone some time and money. I would have never discovered my problem without the other posts on this site. I want to thank everyone for their great posts and helpful advice.
 
Last edited:

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

This is a problem on some of the flywheels from OMC, so they came out with magnet replacment kits. One magnet and the expoxy for it, part number 584304, around $15.00 . If the loose magnet is still good, they sell the magnet epoxy by itself part number 431929, about $6.00. Hopefully, this will correct your problem.
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

i used JB weld around all the magnets that were still in place and also used it to re-attach the magnet that broke loose. i will post the results and let everyone know if it holds. thanks emdsapmgr
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

i put the flywheel back on today and it still seems like i am still getting less spark on 3 of the cylinders (port side) . the motor starts and runs great now on muffs in the driveway. i am going to take it to the lake tomorrow and see how it goes. i am unsure if the problem has been resolved. the stator windings have an epoxy on them that looks like it is melting all over the top of the engine. even though the stator checks out good i am beginning to think that it may be on its way out. i guess we shall see what happens on the lake tomorrow. if anyone has any input that might be of use feel free to post.
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

evrything seems to be ok now. the boat runs good. it is still bogs a bit on acceleration but it catches up after a couple seconds. i am going to make a few adjustments on the throttle and timer base and see if that helps.
 

speedcat2000

Seaman Apprentice
Joined
May 25, 2009
Messages
34
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

how do you tell if the magnets are out of place... I can't see anything but what appears to be one magnet or set of compressed plates that runs the entire circle below my flywheel. 1975 85 hp Johnson - does this motor have the same known issue with magnets?

thanks
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

they will have about a 3/8 gap between each one and if they are loose or broken there will be visable movement.
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

the weak spark still seems to be a problem. i ordered a new stator today. at least once this thing is running i will know exactly what i am dealing with. i am hoping to not need a regulator/rectifier. i must like throwing money into the water.
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

well the staor has cured my boat problems. the clue should have been that there was a sticky black goop running down from the stator in the area where the wires run out of it. it had obviously melted down and was creating an intermittent problem. no that i have replaced the stator the boat is running strong and has no problems. i want to thank everyone who posts. it has made this seem like it was not the end of my boat. for every problem there is a solution.:D:D
 
Last edited:

speedcat2000

Seaman Apprentice
Joined
May 25, 2009
Messages
34
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

great news! How much did you have to drop on that stator?
 

jriegle04

Petty Officer 2nd Class
Joined
Jun 1, 2009
Messages
179
Re: '85 johnson 150 GT loosing spark / weak spark problem solved

Re: '85 johnson 150 GT loosing spark / weak spark problem solved

i found one for 250 from wholesale marine in ohio. everyone else wanted 400.
 
Top