1988 Johnson 120 dying

[PSiedTSi]

My motor has been running great all summer long, only small issues, like needing new plugs. Anyway, put my boat in the water on Friday and was running across the lake at WOT, which is about a 5min ride, so it's a decent trek across a pretty big body of water. Long story short, without warning the motor seemed to lose power "slowly", as in it didn't die instantly but revved down before dying. I noticed it was hard to get it into neutral again. Once I did, it sounded like the battery had died on me, barely cranking. I waited about a min, and it cranked over easily and seemed to run *ok*. It would die at idle but I was able to get it into gear and moving again. It happened about 2-3 more times until I finally made it back to shore(never been stranded before, I felt pretty helpless for a little bit there!!). I figured I would try it again in the morning, hoping I'd have a clearer head and would be able to figure it out. I cranked it up in the morning and it seemed to idle better, but sounded a little deeper. I ventured out for a test run. It felt like it had all the power it used to have, got about half way out again, and it died. The one thing I noticed was it would let out a little squeak as it was dying, or when it died(never once heard the sound before). I decided to limp it to the lift on Saturday while I had someone there to rescue me if I needed it. The boat had barely enough power to get on plane and maxed out at about 4k full trim. It died once during this trip and then I made it without issues after the first dying, but power still was not there.

I took a video of it running, notice the weird squeaking noises. To me, it almost sounds like the timing is wayyy off, somehow. I don't have much experience with 2 strokes, but I know my way around car engires. It feels like the ignition timing is really retarded, but not really sure how that works on these motors. There is a knocking noise in the video, but you can't hear it in person, so idk what that is.

View My Video

Any ideas?

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Bump

 

[dehydrated]

Re: 1988 Johnson 120 dying

First thing i would do is check compression! Then with all the plugs out hand turn over the motor listen and feel if anything is rubbing and where to cause the squeak could be flywheel magnets if your lucky

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

First thing i would do is check compression! Then with all the plugs out hand turn over the motor listen and feel if anything is rubbing and where to cause the squeak could be flywheel magnets if your lucky

Ok, exactly what I was thinking. I'm hoping it's the magnets as well! I've had some battery issues in the past, so I'm hoping it's related *crosses fingers* Although I'm not feeling very confident it's something simple...

 

[dehydrated]

Re: 1988 Johnson 120 dying

Make sure your battery is fully charged for compression test could also be upper bearing which isnt that big of a deal either

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Make sure your battery is fully charged for compression test could also be upper bearing which isnt that big of a deal either

Charged the battery on Saturday thinking it might be something to do with that based on how it cranked right after it died.

 

[Daviet]

Re: 1988 Johnson 120 dying

Man, why are running it with the engine tilted like that, the water pump has to be out of the water and not pumping water to the engine. The carbs will not operate properly at that angle.
As suggested, do a compression test and see what you have, and rotate the engine by hand and see if you can isolate your noise, hopefully you don't have any internal damage.

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Man, why are running it with the engine tilted like that, the water pump has to be out of the water and not pumping water to the engine. The carbs will not operate properly at that angle.
As suggested, do a compression test and see what you have, and rotate the engine by hand and see if you can isolate your noise, hopefully you don't have any internal damage.

The lake is extremely shallow and is having a low water condition right now, any further tilted down and it digs into the sand. The telltale is nice and thick, I always make sure of that. I didn't want to test it out in the lake and get stuck again, so the dock had to suffice. It's not ideal, but it's not like I'm the only person that runs their motor trimmed up...

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Alright, so since I've been going through withdrawal from the forums being down, I was able to do a little testing.

Checked the compression, the numbers were within 10% of each other, all above 110psi...so that made me feel better.

I managed to get some earmuffs last night, and do some test running. I noticed that the oil tank primer bulb felt like it had air in it. I pumped it up solid, and it seemed to stay that way. When I started it up, it was running pretty rough still. I kept the revs up a little bit in hopes it would clear up, like usual. I couldn't get it to idle at all. I noticed when I pumped the ball, it smoothed out. After I did that a few times, I was able to get it to idle without fast idle engaged. Seemed like it ran great, no weird noises that I could hear over the exhaust, cowl on or off. I noticed the ball didn't stay rock solid like it is when I prime it, but I can't say I have paid attention to it in the past. However, it was definitely far from being sucked flat, just a little more spongy than usual. I plan on running it again today and if it runs and idles well without pumping it, I'm just going to call it a weird quirk...maybe an air bubble in the lines? I have no idea.

 

[Daviet]

Re: 1988 Johnson 120 dying

The primer bulb will not stay real firm when the engine is running, should be firm when you pump it up without the engine running.

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

The primer bulb will not stay real firm when the engine is running, should be firm when you pump it up without the engine running.

That's what I figured. Maybe it ironed itself out, just seems really weird. I'm thinking there might have been air in the oil system because someone(OBVIOUSLY not me lol) let the tank run lower than normal. I think the reason it was only spinning up to like 4k when I drove it back to the landing was one of the plug wires pulled off when I put the cowl back on and I didn't notice it until the other night.

I also noticed it smelled pretty lean until last night, when it started running better. Anything else I should check?

BTW, thanks for the moral support!

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Started up pretty nicely today and idled again until I shut the key off. I think the problem is fixed, with basically no diagnosis. I wanted to free rev it a little bit to see if it cleared itself up, but it sounds like the world is coming to an end with just muffs on it. Next step is to water test it this weekend. Is it too much to ask to get out on the water and wakeskate these last couple of nice weekends?? haha

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Well, finally got to do a lake trial this weekend. It ran much better overall. Still a couple of issues tho. I noticed the starter wasn't disengaging and killing the motor when I would try to start it right after putting it in the water and ripping around for a couple minutes. Rowed it back to shore and managed to get it started after pulling the cowl and realizing the starter wasn't disengaging. Didn't really have the issue again the rest of the weekend. It had trouble idling still, and I had to give it a fast idle to get it to start and stay running and slip it into gear before it died. After it was in gear, it generally was ok from there.

The other problem is I noticed I lost about 300rpm at WOT and it didn't feel like the holeshot was all the way there while wakeskating. Usually we pulled each other up with about 3/4 throttle and it was more than plenty. We had to slam it all the way down to get the desired pull. Just really strange behavior from a motor thats given me zero issues the last 10 or so years I've owned it. Maybe dirty carbs?

 

[dehydrated]

Re: 1988 Johnson 120 dying

Have you replaced the fuel hoses? Carb cleaning would be a great start but with ethonal gas today it will break down older hoses cause the jets to clog or worse yet a pinhole air leak I would do both

 

[PSiedTSi]

Re: 1988 Johnson 120 dying

Have you replaced the fuel hoses? Carb cleaning would be a great start but with ethonal gas today it will break down older hoses cause the jets to clog or worse yet a pinhole air leak I would do both

That is a good plan. I think I will do some basic maintenance this offseason. New hoses and filter, carb cleaning/rebuilds. I've owned the boat for about 10 years and as far as I know has only had premium, whenever possible, so it shouldn't have seen *too* much ethanol