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'81 Johnson 115 misfire

T

Turbodime

New member
I have a '81 Johnson 115 on my 24' Flote Bote. This is new boat for us that im half owner of. The boat ran fine 3yrs ago when last used. I charged the batteries and went through both carbs and it started up fine. Took it to the lake and it wouldn’t get over 2200rpm. Took it back home and found the rectifier cable corroded and the rectifier not working, as well as a couple rusted plug wires. I replaced the rectifier, wires, and plugs along with a new rebuild kit on the fuel pump (low PSI) and hose.
I took it back out and it would only get up to around 2500rpm. Took the cover off and messed around with it while running and I thought I’d turn the fuel primer to manual and it was like the turbo switch. The engine went right up to 4000rpm.
Brought it back home and filled a trashcan full of water to do some other testing and this is when I found Cyl 1 wasn’t firing or just sporadic and Cyl 3 had a bad miss. I switched powerpacks and coils and the miss stayed in the same location. I scrounged up a Fluke 189 and tried to test the peak voltage at the orange coil wire as well as the powerpack and stator but the Fluke wouldn’t measure them. I tested it on house power and no problem.
So my best guess is that the stator is bad. I don't like switching out parts just for the sake of it; I like to find out the root cause.
When the engine is cold it starts right up and within a couple of minutes is when the miss starts. It always runs fine at idle cold. I’ve switched coils and the misses didn’t change their pattern.

I have two weeks of working on the boat and not much time in the water. At least here in AZ, the lakes stay over 80F water temp into the end of Sept.
I have plenty of patience but lack some of the tools required to really troubleshoot these motors. CDI and this website have been a great help. I have learned more about outboards in the last two week then I have all of my 44yrs of life.


Thnaks for your time.
Aaron

p.s. this is my first post and I hope I can help out where I can.
P.s.s I have a Johnson engine manual:)
 
Last edited:
You state: "I thought I’d turn the fuel primer to manual and it was like the turbo switch. The engine went right up to 4000rpm."....... That should tell you that fuel isn't flowing thru the carburetors properly.

You've overlooked something within the carburetors..... possibly the horizontal high speed jets located in the center bottom portion of the float chamber(s).
 
joereeves said:
You state: "I thought I’d turn the fuel primer to manual and it was like the turbo switch. The engine went right up to 4000rpm."....... That should tell you that fuel isn't flowing thru the carburetors properly.

You've overlooked something within the carburetors..... possibly the horizontal high speed jets located in the center bottom portion of the float chamber(s).
Click to expand...


I agree with that. I cleaned the carbs in the wrong order. I cleaned them then I ran it on the lake before I rebuilt the gunked up pump and hoses. When I was in the carbs I did find an emulsion tube with a hairline crack. It looks like these are pressed in but I thought I'd run it before repairing or replacing the carb.

I know I have an electrical miss. Ive confirmed with a timing light and a spark tester.
 
Hi Turbodime.

To add to joe's point, i think you may have more than one problem resulting in a motor that won't go to WOT properly.

From what i have read, i would suggest doing carbs again, making sure that everything is 100% and then before running it go through the electrics.

You say you replaced the plugs and plug wires. Did you also swop the plugs and plug wires to different cylinders like you swopped the coils and powerpacks? It's not unheard of for plugs to fail almost out of the box, if you have that's another thing off the list to check.

I'm not 100% sure that your stator is at fault. Have you gone through the wiring completely checking for loose connections. I have same year motor as yours in a 90hp. At one point not all of the connections were forming correctly within the rubber connectors. I ended up removing all wires from their boots, cleaning them and checking for the right fits between wires on the connectors. Some of the connecters had somehow expanded and weren't connecting properly. I made sure they did and put back in the rubber boots and that got rid of one of my problems. From the powerpacks to the coils i actually removed the boots and joined them with a different type of connector. One way to check the wiring without removing from the rubber connectors is to move the wiring around with a wooden dowl when the motor is running as the movement may complete a circuit.

Is your battery charging with the new rectifier?
 
I've did the taping on the connectors tonight and no luck. It still starts easy and runs great until it heats up and then wam. The engine has a fresh power head with 140ish psi but they put all the old electrical back on. I may just breakdown and rebuild the wiring harness. All the amphenol connectors have grease in them hope it's dielectric grease. If I had the handtools to to take the puns out I would do that and clean them but when I was testing the kill switch I ripped out one of the pins.
I may just cut the connectors out and put new ones in.

Thanks for the advice.
 
Just back in from checking all connectors. Cut out a couple of the connectors on the side that has the miss and I still have the miss even without warming up. The Fluke 189 definitely wont grab any readings from the stator or powerpack in peak voltage mode. I tested the brown to brown/yellow and I had 35VAC to 55VAC. Don't know if this is even a viable reading without a DVA? I'm going to pull the flywheel and see if anything jumps out. I'll post more later. I plan on following through with this until I find the issue(s) that's causing the miss.

New rectifier is charging batt at 12.8v at idle on muffs.
 
Great news on the rectifier. I'm sorry to hear the base problem is still there.

From what I know getting the correct readings from the stator requires a meter that can measure DVA or a DVA adapter. I haven't got one and they are pricey down where I stay. There are resistance checks you can do to check the overall condition, but my motors readings are not what the books says they should be and it runs fine. Sometimes a black residue under the flywheel indicates a bad stator, let us know what you find when you remove the flywheel.

When you said the cylinder wasn't firing did you determine this by doing a "spark check" on the cylinder without the motor running with a spark tester jumping 7/16" gap or a "drop test" when it was running?

A drop test on a running motor can also be caused by a clogged carb and there was a post by someone else this week who had a bad carb which showed up pretty similar to your problem in a drop test. He switched carbs and the problem moved...
 
I was hoping the 189 would read it as I have read this on the Internet but it doesn't. Checked resistance on all wires and coming from the stator I'm getting 155ohms when CDI says it should be max of 55ohms. This is white to green wires. All others within specs. I used a spark tester at proper gap and even pulled it in tight. Also checked with a timing light. Have to make a proper puller tommorow. The journey continues.
 
I was wrong on the 155 ohms coming from the stator, its the timer base white to green wire with the 155 ohms. The higher then spec resistance is on the side which is having the miss.
 
I'm not 100 sure what that means but it does warrant further examination. let me know what you find when you have the flywheel off
 
Flywheel off tonight. Checked all connections and wires and didn't see anything amiss. Re-checked resistance on that one odd reading from the timer base and it wasn't 155 ohms it was 150 Mohms. Took the timer base off and cut back the protective sleeve and found 4 of the 6 wires were previously hit by the flywheel and haphazardly wrapped in electrical tape.
I carefully took the old dried tape off and I found a strand of wire touching another wire, both from the same side that has the miss. I separated them and once i did this the 155Mohms went to open

Looks like I need a new timer base. Once I get one and installed I'll post my findings. I'm going to go back through the carbs like joereeves suggested as well.

Thanks for your help.
 
Thanks for the update. i'm glad that you've found the problem. There are quite a few posts on the site about the flywheels not being tightened to the correct torque when they are replaced. As a result they spin and sheer the flywheel key causing all sorts of different issues. Getting it up to the right torque when you replace is going to vital to keep it running properly. Let us know when it's done and good luck.
 
Ouch!!!! I just saw the price of the timer base. Sorry for the loss to your bank balance.. And I can understand the previous "patch" job. This is one of the good reasons for multiple ownership of a boat....
 
Picked up a new to me timer base from Ebay (outboardmotordoctor) it was a winner and is running top notch minus the carb issue. I'm working on that this week.
 
Picked up a new to me timer base from Ebay (outboardmotordoctor) it was a winner and is running top notch minus the carb issue. I'm working on that this week.
 
Took both carbs apart and found three of the four high speed jets plugged with old fuel/oil. Cleaned and reinstalled. Im going to stick 2 new plugs in because they were fouled from not firing due to timer base issues. Got the stero and lights working and we're headed to lake Pleasant this sat for some testing. Thanks for the help guys.
 
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