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Johnson 15HP 1979 no spark.

V

vlad1977

Member
Hi guys, I just joined the board and need a hand with trouble shooting my outboard.
About the engine. I believe it is a 1979, Johnson Seahorse 15 HP. I see raised mark "9.9 J" on the inside of the top cover, then it is written by the sharpie "Jonson Seahorse 15HP". I believe the later is correct, just to be sure the label on the mounting bracket reads 15EL79E.
The owner of the marine shop (who is an official Johnson dealer) is certain it is a 9.9 HP model.

Right now I have no spark in both cylinders.
The motor was pretty hard to start ever since I got it with the boat (4 rides so far). Once started it would work fine in mid-throttle, going full throttle would make it shut off in a few minutes. After the engine shuts off it was nearly impossible to start it. If wait for an hour or two - it would start again.

During out last trip it stalled and after that it would not start at all. Not even a bit. I transported the boat home, unplugged spark plugs one by one and tested them one by one out of their cylinders. One was giving a spark when I was pull-cranking the engine. The other was not. The sprarking issue did not travel with the spark plug and belonged to the coil of the cylinder on the top.

I ordered an ignition coil thinking that this is the coil issue. After assembling of the new coil in place I tested spark plugs and none of them was giving spark now. Then I ordered and replaced the power pack. I really hoped that that was the power pack. But no result!!! I do not see the spark.

Where should I look next?
Thank you!
 
Can you disconnect the kill switch and try it again. I think it might just be clipped together. Just unclip it and check for spark.
 
optsyeagle said:
Can you disconnect the kill switch and try it again. I think it might just be clipped together. Just unclip it and check for spark.
Click to expand...

My motor has a kill button, not the kill switch with lanyard. I tested the continuity of the button with the ohmmeter. When not pressed it has no continuity. Is this sufficient or should I remove it?
 
vlad1977 said:
My motor has a kill button, not the kill switch with lanyard. I tested the continuity of the button with the ohmmeter. When not pressed it has no continuity. Is this sufficient or should I remove it?
Click to expand...

It's possible that it has an intermittent short. Disconnecting it would be the true test. If the problem is still there, it is not the kill button.
 
I got the spark the sparks. The problem was I was testing the spark plugs without ones touching the ground. it is strange but it was working like this before, I mean that the spark plug gave the spark without touching the ground. when I'm thinking about this now it doesn't make any sense to me that the spark plug would give a spark without touching the ground, but this is what I saw.
Primed each cylinder with a few drops of gas, tightened the spark plugs.
Does not start. I have not done a compression test yet, left it for tomorrow. Any things where I should look into first?
 
Get a spark tester and see if it will jump at least a 1/4 gap, if not spark is weak, If spark is weak look for stator problem.
 
Compression test returned 90 psi for both of the cylinders and looks like the harder I pull on the cord the higher was the reading. It might as well be a 100 if the motor runs on its own. Opened and checked the fuel filter, nothing special, cleaned out a few dust particles.
Well, pulled the cord again one time and the engine nearly started!
Good thing actually it didn't, because it was 2am and I didn't want to wake the neighbours. :)
The thing is, I don't think I fixed anything.
I will try to test the stator with plug tester as Faztbullet suggested and hopefully I don't have to replace the stator. BTW, how do you guys immobilize the flywheel while undoing the top nut? I realize I will need a harmonic balancer removal tool to lift the flywheel, but I have to undo the nut on the top of the flywheel and the torque is pretty high there, while the flywheel is spinning freely.
 
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I use a strap wrench to hold the flywheel. If you don't have one big enough you can build one out of a piece of wood and a nylon strap at the end. I have also use an old electrical extension cord attached to the end of the wood. Just make sure the wood is at least 1" thick. It takes a lot of force to hold back that flywheel and anything thinner may just snap.
 

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Thank you, guys.
On Sunday my friend and I removed and cleaned carburetor, blew the air through every hole we could get access to. It was clean to begin with except for a rusty spot at the bottom of the reservoir. Cleaned that out. Confirmed the flow of the gas to the carburetor.
Does not start!
Occasionally it sounds like it starts, but then dies again. If it seats with the choke lever pulled for awhile, or if I squirt a few drops of gas inside the cylinders, the it may run for a second and then shuts down before it has a chance to stabilize.
The gap tester return about 1 inch at which I can see the spark between leads.
Under the flywheel I see the stator that doesn't show any blown wires or other damage.
What else can it be?
 
Kimcrwbr1,
Thanks, sounds like I did not clean the carb properly. I did not soak it, just took it out and cleaned with brush and gasoline. This carb does not have any dedicated jets, just 3 tiny holes.
Another question. What if there is not enough vacuum? For this I will need to check the main block and pistons? When it comes to that point I will research more, just want to know in general right now. Chances are it's vacuum.
 
Update.
After the long winter I finally removed the carb, undid everything on it entirely including all the welch plugs and cleaned out with carb cleaner. There were no obviously clogged passages.
I replaced the plastic parts around idle pin.
Closed all holes with lead or welch plugs from the maintenance kit.
The carburetor could not be any cleaner now I guess.
Put everything back. Pumped the gas into the carb. Primed the carburetor with the carb starter. Still no start.
Now I know it's not a carb and it's not the spark plugs/coils.

I tried to start the engine with electric starter. This gets it started, but as soon as the electric starter disengages from the flywheel the engine dies. Electric starter starts it, then the engine makes the flywheel spin a bit faster which causes the disengagement from the electric starter gear and a second later the engine dies before it reaches normal revs.

I know that when the engine was working it was let run on regular gas (without adding the oil).
What would be the next thing to check? I measured the compression and it is about 90. How do I check for proper vacuum?
Thank you
 
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Johnboatcaptainron said:
Stupid question, but maybe simple solution, was the keyway in it? Sounds like it is out of time. Maybe it broke.
Click to expand...

Do you mean the keyway under the flywheel?
Yes, it's in there. I removed the flywheel to check for any signs of electric shortage. Everything looked fine. I don't know how to check the points, but visually everything was fine. So was the keyway. The engine stopped working before I lifted the flywheel, it didn't change after I checked in there.
 
Are you mixing gas and oil at 50:1 ?------------Have you checked for proper cooling / replaced the impeller ?---------Have you done a compression test ?--------Have you checked for spark with a test device and a gap of say 1 cm or more.---Checking for spark at night is best here.--------Have you checked the reed valves ?
 
racerone said:
  1. Are you mixing gas and oil at 50:1 ?------------
  2. Have you checked for proper cooling / replaced the impeller ?---------
  3. Have you done a compression test ?--------
  4. Have you checked for spark with a test device and a gap of say 1 cm or more.---
  5. Checking for spark at night is best here.--------
  6. Have you checked the reed valves ?
Click to expand...

  1. The gas is mixed now 50:1. But in the past I used the plain gas w/o oil for several trips (20-40 mins each). The engine is not stalled, I can crank it and it is able to turn a few cycles by itself before it dies if I use an electric starter.
  2. No, but it was never let run out of water and the expelling water was fairly hot (not the boiling temp, but far from cold);
  3. Yes. Around 90psi.
  4. Yes. Good sparks with the gap of I'd say 2 cm at least;
  5. No. How do I check those?
And another question. How do I check for proper vacuum?
 
You really need to evaluate this motor if it has been run on straight gas with no oil.-------5 minutes might be ok, but an hour or more ???????????
 
racerone said:
You really need to evaluate this motor if it has been run on straight gas with no oil.-------5 minutes might be ok, but an hour or more ???????????
Click to expand...
Yes, I regret my decision into jumping into the water without bothering to check for type of fuel.
But, I hope i can figure out and nail the issue with the help from you guys.
 
Update.
Today me and my friend managed to start it! Woo-hoo!
It all happened almost by accident. I got new spark plugs (Champions", removed one of them to check if spark is still there. The spark was, but the same time as we were checking on the spark the engine started running (on the cylinder#2). We tried to see if it would run on #1, but it wouldn't.
With 2 spark plugs it was much harder for the electric motor to crank the engine, seems like the battery is weak. Went to the Wal-Mart, got a 800 cca battery. It indeed pushed the electric ctarter harder, but got no start this time. We thought that this was related to the magneto heating up (we had that no hot start in the past), but I checked the priming bulb and it was allowing me to pump gas to the carb in the amount that exceeded my expectations. Once primed, the engine would start again.
Now we checked the compression.
#1 cylinder = 98 psi, #2 = 110 psi. Both sparks are blue. Swapped the plugs - the cylinder #1 is not running.
I'm thinking, maybe this is related to compression?
Do you think adding more oil to the gas would increase the compression and would help to confirm the source of problems?
I took a video of the motor running. When it's left running on the cylinder #1 alone it is slowly dying. Not abruptly, but slowly. I have not played yet with lean/reach knob.
 
kimcrwbr1 said:
Swap the coils around and see if it follows the coil? Your compression is within spec of 10%. It could be a reed valve or a bad upper crank seal.. You cannot test spark with the plugs you must use a spark gap tester. It should jump a gap of at least 3/8 inch brite blue snap. 50:1 oil mix is all it needs so confirm it is getting good spark on both wires. It could also be a leaky transfer port cover gasket Fill a bottle with soapy water and spray it all over the powerhead while it is running looking for bubbles.
Click to expand...
Last year I tested it with a spark plug tester. 3/8 of an inch was easily achieved. I'm not sure if it was a blue spark, but I was able to get the spark over one inch long. Not sure if this was a meaningful result.
I'll try that soapy water test. Hopefully it's not something with power head.
 
kimcrwbr1 said:
Your kidding right. You cannot go by last years spark gap test. Confirm your getting good spark before going any further. Anything over 90 psi on these motors and they will run with good spark and fuel precharge in the crankcase. You can replace the upper crank seal, reed valve or bypass cover gasket without pulling the powerhead. If your gettin good spark it is one of those three all of which may be the reason the top cylinder compression is a little lower.
Click to expand...
Ok, got a bit more time and convenience of typing from desktop.
I tested sparks last year in october when I started to working on the engine. The engine was not run after that, so it's very unlikely anything changed since then. But it takes a minute to run the check, so be it. Will do tonight.
Now, the next thing I guess would be to sprinkle the soapy water and observe for the bubbles. If there are no bubbles, it's time for replacing reeds due to the age anyway, right?
For that I need these parts - 52, 53, 51, 49 and 2x 48. (2 reeds, manifold gasket, plate to crank case gasket, reed stop set and a shim) on this picture
08.jpg
I found this kit on ebay. Not sure what it has in it for $25. Just emailed seller.
I am kind of inclined to replace it anyway. Age of the engine, my curiosity. Please warn me if I am going wrong route ))
 
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