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lotsofish

Johnson 35hp

9 posts in this topic

Over the past few weeks my 1973 Johnson 35hp has been giving my some problems and I just wanted to mention what it was doing and what I've done that's helped(temporarily) so that if anybody has had the same experience can chime in or anybody else can let me know if they think I'm on the right track.

First I'll start off with what it's doing. It will run normally, have all the power it's always had and work just fine at times. While running normally and cruising on plane, it will start to lose power slowly, then all of a sudden drop power very low. It may do this for a short time, then run normally for a second, then back to slow, creating a jerky ride. Soon though it will get "stuck" running poorly and sound bad. It's only running on 1 cylinder.

I tried changing the spark plugs as a first step, but it has not made any difference.

If the motor is running "bad" I can take the cover off, remove the spark plug wires and reconnect them or sometimes just jiggle them a bit and it will work again for a little while, which makes me think that the problem has to do with the plug wire connection. I have tried to use a pliers to tighten the connector inside the plug wires and it seemed to work for a little while, but while out tonight the motor was doing the same thing. I was able to fix it temporarily again out on the water, but after doing it about 6 or 7 times it got to the point where I couldn't get it started.

When testing it in the driveway, I've tried to start the motor with only 1 plug wire attached to see if I could reproduce the effect/sound of only 1 cylinder firing or to isolate which cylinder is having a problem, but I could not get it started that way. With the plugs out and wires attached, pulling the starter cord does create spark in both plugs, but I don't know for sure that when I tested it if the motor would have been running normally at that time or not.

I would just replace the plug wires and try it out again, but the problem is you can't replace just the wires on this motor. They come out of a coil pack directly and I would have to replace the entire coil pack too just to replace the plug wires. I haven't tried to find one yet, but I'm sure I'll be looking at finding a used one since this is such an old motor. Before I go buy the piece and try it, I just wanted to see if everyone thinks I'm on the right path or if there are any other tests I should try first.

Thank you.

Edit: In doing some looking online, it might not be a 1973 motor since I don't think they made a 35hp that year. I will check tomorrow to see for sure, but it is from the 70's.

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I would be tempted to go the direction of the coil pack. Maybe call around to a few marine bone yards and you may be able to find a used one. I would check online.

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I concur w/H.Lee's assesment. If a good outboard shop is handy it might be time for a trip to see them. wink.gif

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A simple way to see which cylinder is dropping is to run it with a timing light connected to either plug wire and observe the light and listen to the motor. the light will go out or flash intermitantly. switch to the other cylinder if you need to. Be sure to route the wires so they don't get caught in any moving parts. As the stator plate rotates, the plug wires are also moving, possibly shorting somewhere to ground. It may also be grounding to the hood latch. Check for wore spots in the wires, or cracks or burned spots on the coils.

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i had an old johnny that where the plug wires plugged into the pack there is a two pin connector that one of the two pins had not been properly been plugged in and when it would run for a while it did the same thing you describe. i had one of the best outboard motor men totally stumpped for about three hours and when i left he was beating his head on the wall for it being such a stupid thing not to check first. we both got a laugh out of it. ... paul

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Quote:

i had an old johnny that where the plug wires plugged into the pack there is a two pin connector that one of the two pins had not been properly been plugged in and when it would run for a while it did the same thing you describe.


I think mine has the same thing you describe. I'll have to mess around with that first and see if that's it, but I have a feeling it's either in one of the coils itself or in one of the wires that connect to the plugs. I did find a couple sources online where I can order new coils/wires, so I might end up trying that if I can't get a really good price on a used one at TC Outboard or something first.

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What is the model # of this motor? The tag should be on the transom bracket.

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The model number... something like 35RL78?? - So it's a 1978 engine.

I decided to replace the coil packs with new ones (which includes the plug wires). I could have saved a little by ordering online, but I wanted to do it right away instead of waiting 3-4 days, so I bought replacements locally. I took it out for a 10 minute ride last night and it ran good without any sputtering or power loss. smile.gif

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Lotsofish,

I have been pegged with the same concern you have this summer. My motor would run great after launched and a little up stream I would lose power and die. After a little wiggling around, it would fire up and run great. I know it is two concerns, because the housing hold down screws for Disp. cap came loose and ground inner posts. I got a new cap and it started and ran fine. Well, a couple of weeks ago I brought boat down to a FM get together (started before I left home, at bro in-laws house and at gas station and ran great) launched boat and wouldn’t ya know, right in front of about 6 other FMer's it would not start. So I floated down stream to area we were fishing (With reassurance from a couple FMers I would be towed back), fished for awhile and figured I would redeem my self and the night. I removed hood again and checked with test light to make sure Ignition switch powered back to motor. Pulled spark plug and found dry as a bone. Then one of three things I did made it run great.

1) Wiggled coil wire to cap. Loose or corrosion.

2) Wiggled slightly loose connector on coil (white wire).

3) Squeezed the gas bulb a good couple of times (because of dry plug).

I did not even have to choke it, she started right up and purred liked a kitten. By then there were 20 or so FMers on shore and all I can remember is a cheering row from all of them. My night turned around. It ran great all night then, until right before we loaded up. It did it again. I just used trolling motor to get back to launch and loaded it up.

The next morning with out doing anything to boat, it fired up (possibley 2 hour drive home, bouncing). I figure I would replace coil, clean connection and tightened. Replace coil wire. If it is a fuel concern, work that out later

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