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1980 Johnson 35 troubleshooting J35ELCSM

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Bock16

New member
I am looking for suggestions on what to look for please. I've only had this new to me boat out 3 times since July.

1st trip: No issues, ran great
2nd trip: No issues, ran great
3rd trip: Right off the trailer engine would fire then pop and die over and over again. No throttle response whatsoever. I ran off the trolling motor for a bit until the sun came up and didn't do anything other than poke around at stuff on the engine. Fired up and ran for the next few hours. Starting, stopping, high rpm, low range etc. etc. I burnt probably 4 gallons running all over the lake. Then it started cutting out and bogging down under load. I changed the spark plugs with no change.

Got it home and decided to start taking a look. (I'm new to OB's, but somewhat mechanically inclined) Wiring was done very poorly with bad connections and too many splices, even a wire nut! for my comfort level. Two different styles of coil w/ one being much older, very old fuel lines/hoses. I decided to give it my best and throw some preventive maint at it since components like the power pack and coils had exposed wires and things. Don't knock me for replacing parts.. was going for the benefits down the road of having new components installed.

Here is what I have done:

-Rebuilt Carb, No residue or buildup present, yes I pulled the high speed jet and cleaned it w/ carb cleaning wires. Soaked for a few hours in chem dip and washed off with water and blown out through the passages. The mixture screw was not 1-1/4 turns out. I lost count, but it was in the neighborhood of 5 turns. I did not remove the lead plugs, possibly my issue now.. please keep reading.
-New Coils
-New Powerpack
-New fuel pump/gasket
-Adjusted throttle linkage per the manual (it previously was not opening the butterfly fully)
-New fuel line and oil return/telltale line
-Wiring issues resolved and poor connections corrected
-New primer bulb/hose
-Gas tanks drained and filled w/ fresh mix

After all the work, I cranked the engine on muffs in the driveway. No go. Choke in, choke out, no difference. It's an electric start converted to manual choke.

-Compression on both cylinders was 110. Read 120 when I brought it home, not sure why the different reading.
-New Champion plugs gapped @ .40
-Spark test showed a thin ~1/64"-1/32" blue/white spark reaching 7/16 on a gap tool. (It was in the sun and I was shading it with my hand) It's hard to tell how thick the spark was since it isn't a straight line, but I was expecting a fat 1/8" lightning bolt based off some of the responses I've read. Is this concerning?
- Fuel bulb got rock hard.

Still not even a hint of pop bang happening. I set my idle mixture screw at 1-1/4 as the air box sticker tells me to so I started turning that screw further out as I remembered when I took the carb apart it was no where near 1-1/4. Got to about 3-1/2 turns and it started popping then dying. Finally settled at 5-1/2 turns out and it stayed running. 5-1/4 turns out and the idle sped up a tad. Now it starts runs and responds to the throttle (still on muffs). Let it run for a few minutes with good telltale water and the idle was hanging right around 900 rpm. All of a sudden it drops 200 rpm then comes back up. Then drops again a few hundred. Basically running like crap. Turned it off and put it away for the night.

Other than rebuilding the carb again, which I just did is there anything else that could cause my issue? Is the spark as I described acceptable?
 
If you have the idle screw out that far you have some issue for sure.Should be flooding or really RICH at idle I would think?Did you pull flywheel and check key?Did you remove welch plugs?Saw you did not remove lead plugs.Go on CDI electronics website and they have some troubleshooting steps for the electricals.
 
I didn't remove the welch plugs. I'll take a look at CDI and see what they have. I haven't checked the flywheel key either. I figured if that was sheared it wouldn't run at all.

Any other ideas? Keep them coming please.
 
The flywheel key is in place, although I was surprised that there isn't a lot of meat on that thing. I double checked compression and spark as well on the motor while cold and got 122/125 for compression and now I see what the snappy spark is that is being looked for.

Tomorrow I am going to pull the carb off and pop all the plugs. Is there a carb tutorial on here or anything? It's such a simple carb I didn't think I missed anything last go around but obviously something is still plugged since I have spark and pressure.

Feeling kinda "monologuey" on this thread, maybe the first post was too long/descriptive - dunno but I'd appreciate any feedback, even if it's that I'm up the creek w/o a paddle.
 
Fact------The flywheel key is there to put the flywheel in the right position for spark timing.-----The flywheel is driven by the locking tapers.-----That is if the tapers are in good condition.----Clean and dry.----Proper torque on the nut.-----What oil are you using at 50:1 mix ?----Have you installed a new water pump impeller ?
 
I am using Super Tech 2 stroke mix oil. I bought the boat a few months ago and got a receipt for water pump and impeller change dating Nov 18'.
 
Today I rebuilt the carb again and popped the core plugs out this time. Put it all back together and the rpm hunting has cleared up. I started out at 1-1/2 turns on the mixture screw and sure enough ended up at 5-1/4 again. 5 turns and it would die out. 5-1/2 and it got a little rough.

I am thinking maybe the needle was swapped out from another carb possibly. I have no idea. Common sense tells me that if 1-1/4 is the target range then I most likely have a parts mis-match. I can't think of anything else, can you?

Here is a video of it running.

 
As seen on the video in post #8 the engine will run on muffs. I went to the lake yesterday afternoon and learned that I still have problems.

I tried to fire it up after backing down the ramp and there was no fire at all. Choke closed, open, didn't matter. I messed with the mixture screw after not getting any combustion with no better result. Only thing I noticed was that when I first tried to fire it up, there was a little bit of spitting out of the exhaust (Air?) After messing with it for a bit, I pulled the plugs and they were soaked in gas. I can only assume that this is due to my idle mixture screw being 5-1/4 turns out. I tried a set of used, but dry plugs and there was no change. I also noticed that the water at the ramp was beginning to shine with fuel/oil so I quit and dragged the boat back home.

Spark/Compression/Fuel have been addressed. I think that I need to figure out why my idle mixture screw is 5-1/4 turns out to run. Is there a gasket that I need to be looking at that would cause a lean condition where the 5+ turns would be the compensating bandaid? When I first had issues, the previously well running (at 5+ turns out) engine started backfiring through the carb on cold startup in the lake. Then it ran fine for a few gallons of gas and began bogging down at high rpm.

Not sure where to go from here.. Any suggestions at what to look at?
 
racerone said:
load test the battery.-----Pull starter apart for inspection.
Click to expand...

Racerone, are you thinking the starter isn't spinning fast enough?

I ran it in a barrel at home today rather than muffs and am not confident the spark is satisfactory. The spark looks to be more orange than blue to me. Can you let me know how it appears to you? I also did a drop test and it would not run on either cylinder solo.


 
I believe the problem(s) are solved. I took it out to the lake and started out at 5-1/4 turns on the mixture screw. Choke closed, pop bang die. Choke open, pop bang die. Tried again giving it a little throttle and it idled on the trailer and stayed running with the lever down after a minute of warming up. I think the key is that I started out with the mixture screw at 5-1/4 rather than working my way up from 1-1/4 resulting in flooding, which I think is the issue from the last lake test. Ran up and down the lake for about 30-45 minutes at different throttle positions with no bogging, no surging and nothing else out of the ordinary. I put a few oz of seafoam in my gas tank as well, as I have come across many posts advocating for using this treatment.

- Did anyone watch my spark videos in post #13? I would really appreciate an experienced opinion as to whether the spark should look differently (more blue etc). Obviously the engine runs so it must be close, if not right...
- On the lake the tach was reading 4000/4200 and pushing the 16' super sport at 20/20.5 mph. Should I be expecting more?


My kid took this video of the boat running - his head is on a swivel.. sorry.

 
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