1995 40HP Johnson Power Problem

[dalliod]

I just bought a 1995 40 hp Johnson. It was converted to a tiller, the oil injection has been removed and now just uses a 50:1 fuel mix. I just used it for the first time and it worked great for about 30 seconds. Got on plane a was cruising along. I slowed down for a second to tell my dad to hold on to his hat and when i tried to throttle up again the power was not there. It seemed to have the power of a 10 hp. A day later it seemed to drop down again in power about an 8 hp. It starts up and idles well. When I bought it the compression was 150 in both cylinders. It uses an electric start and electric choke. I have it on an AW 1860 mod v alumacraft jon. The gas was brand new and I just changer lower unit lube. Also installed new plugs. My friend checked spark and said it was good. It is my first boat and outboard. Any help would be greatly appreciated.

 

[nphilbro]

Re: 1995 40HP Johnson Power Problem

First, check the choke switch to make sure it's in the "auto" or "run" position...not sure what it says. If it's on "manual" or "start" your air/fuel mix will be way off and cause this. I'm referring to the lever connected to the carburetor. When you press the key in it should "click" when the solenoid activates the choke.

What plugs did you replace the old ones with? These motors are quite particular. Beside the obvious issue of whether it still has good compression, is how did he check the spark? Grounding the plug only tells you there's current but nothing about the the quality of the current.
If compression is good (check again), spark hits 1/2" on the tester, new plugs are factory brand and spec/same issue with old plugs (don't automatically assume the ones you pulled out were the correct plugs) you can move on to checking fuel issues. Check the cheap and easy stuff first. Easiest of all if this happens while under way- squeeze the primer bulb to see if it surges (fuel pump would likely be culprit then).

On my larger motors I've had the fuel line collapse under load but I doubt that's the problem here. Even if it's restricted somewhere it could cause that but it would drain the carb float bowl before cutting out.

 

[dalliod]

Re: 1995 40HP Johnson Power Problem

First, check the choke switch to make sure it's in the "auto" or "run" position...not sure what it says. If it's on "manual" or "start" your air/fuel mix will be way off and cause this. I'm referring to the lever connected to the carburetor. When you press the key in it should "click" when the solenoid activates the choke.

What plugs did you replace the old ones with? These motors are quite particular. Beside the obvious issue of whether it still has good compression, is how did he check the spark? Grounding the plug only tells you there's current but nothing about the the quality of the current.
If compression is good (check again), spark hits 1/2" on the tester, new plugs are factory brand and spec/same issue with old plugs (don't automatically assume the ones you pulled out were the correct plugs) you can move on to checking fuel issues. Check the cheap and easy stuff first. Easiest of all if this happens while under way- squeeze the primer bulb to see if it surges (fuel pump would likely be culprit then).

On my larger motors I've had the fuel line collapse under load but I doubt that's the problem here. Even if it's restricted somewhere it could cause that but it would drain the carb float bowl before cutting out.

The motor was converted from remote steer to a tiller and has a push button electric start. It also has a rubber push button electric choke. There are no labels on the choke button. I just push the electric choke button and then push the electric start button and it starts right up, there is no key. If it is warm I can usually just press the electric start button and it will start up without the choke being used. I replaced the plugs after the problem started with Champion QL78C. I just double checked and it is the mfg recommended plug. I did try to squeeze the primer while the engine was running in forward gear but I saw no difference. The tank is an older metal johnson 6 gal. I also tried running with the cap on the tank loosened but that didn't help either. I believe my friend checked the spark by just grounding it. I just had to get stitches in my hand so as soon as Im able I will do another compression test and proper spark test.

The guy I bough it from said that he had only run it with muffs on and never lake tested it. He said he had been told it wasn't used in years and has extremely low hours. When I got it he said the spark plugs were the original plugs. When he pulled them out to do the compression test the were perfectly clean but they did have a tiny bit of black oversprayed paint on them. After I had the problem and I took the plugs out they were already black and my friend said the engine was flooded. I emailed the guy I bought it from and he said it sounded the clogged secondary jets.

What octane gas is recommended? I used 87.

I will post compression and spark results as soon as I can.

Thanks for your help

 

[nphilbro]

Re: 1995 40HP Johnson Power Problem

I'd be looking at the choke position first, now. Most will start when warm without the choke but not well, if at all, without it. While engine is running, if you "activate" the choke, will it die, sputter, speed up, or does nothing change? If nothing happens then the choke lever is probably in the wrong position and just needs to be flipped so the choke solenoid will close the butterfly when activated.

If it's not that then I'd start looking at the high speed jets. You can download the carb parts diagram to locate them and make sure they are clear (if fixed) or open to spec (if needle adjustment). There are a few other possible culprits once you rule these out. Eventually you could look up Joe Reeves "Link n' Synch" down the line but start with easiest first since it's usually the most likely culprit. These motors are pretty simple once you get an understanding but there is certainly a learning curve. You'll be glad you spent the time to learn since it will salvage those spare moments of fishing time.

 

[dalliod]

Re: 1995 40HP Johnson Power Problem

I tested the compression and it was about 148 - 150 in both cylinders. I tried to test the spark but i didn't get any spark at all. Im not sure if I'm doing it wrong or if the tester i bought is messed up. Is it ok if i ground it to a painted bolt or do i need to find something without paint on it? Do i need to take the plugs out to test the spark? Should both boots be pulled off? I just pulled the boot off the plug, attached the tester and put the clip on a bolt on the block. Then I pushed the starter but i didn't see any spark, even when i shortened the gap to about an 1/8 inch.

Im not sure how to check the choke position. There is only a rubber button. There arent any different positions you can set it to that I can tell. It just has two wires coming to the button. Each time I press the button I can hear 1 click but I don't see any moving parts.

When I pulled the spark plugs for the compression test the top spark plug was pretty black and the bottom one was clean. Both are new. Not sure what that means.

I also need to get some muffs so I can see what the choke button does to the motor while its running.

By the way the first compression tester in loaned from auto zone read 90 psi. I was a bit nervous and decided to double check it so i got one from pep boys and then it read around 150 which is what it was when i bought it.

 

[nphilbro]

Re: 1995 40HP Johnson Power Problem

Regarding compression, the consensus seems to be all testers are different. The two readings are near enough it shouldn't an issue at all.

For spark test, this guy lays it all out very well and wouldn't be any different for your motor. We fish the same waters and I've learned an incredible amount from him.
Maintaining Johnson 9.9 Troubleshooting

To answer your question, the clip on the tester needs to be ground to the block. I usually hit one of the head bolts. If they're painted, make sure it bites through the paint.

You didn't mention the model number. Found a parts diagram it appears to have a primer vs. choke so we can scratch that - common problem on some other motors. Can you share what model it is?

When you say "black" is it wet or dry black? Gunked up or carboned up?

I think you need to rule the spark issue out before moving on. Make sure the plug wires are attached to the right coil. Not sure if they can be switched on this motor but it's worth checking. Also check the connection between the coil and powerpack. Again, not sure if they can be switched. While at it, if there's a fuel filter inline, make sure it's not clogged.

If spark tests out fine, probably start looking into the carb. Could be as simple as an air leak from a bad gasket. Just want to rule the easy stuff out first. Get some Seafoam at the auto store and put it into the tank.

Were you using a clean gas tank with new fuel? Water or grit running through will raise he!! with the fuel system.

If you start to make progress don't spray starter fluid into the carb, just spray a bit of fuel/oil mix.

 

[dalliod]

Re: 1995 40HP Johnson Power Problem

Cleaned some paint off the bolt and the spark was jumping the 1/2 gap with a blue spark just fine. I looked at the blackened plug more closely and it was wet. It had a tiny bit if gunk in the corners where the side electrode meets the threads. I smeared it on a paper towel and it had some very fine metal powder and a couple metal flakes about half the sized of a black pepper flake. It also had maybe three hard black flakes, the biggest was about the size of a black pepper flake. The black flakes broke apart easily. The fuel filter looked clean. The gas had about 1/2 gallon of 3 week old gas in it(according to the guy I bought it from) to which I added 5 gallons of brand new gas and 13oz of mercury quicksilver brand 50:1 oil mix. J40ELEOD is the model. I am going to try a post some pics now.

 

[dalliod]

Re: 1995 40HP Johnson Power Problem




Here is the blackened spark plug after I wiped it of. Should have taken pic before. Not sure if you will be able to see metal flakes on paper towel.



Primer button and electric start button is on bottom left side of shift lever



Throttle wide open



Carbs

 

[dalliod]

Re: 1995 40HP Johnson Power Problem



Throttle as low as it goes



Fuel filter



Plugs

 

[dalliod]

Re: 1995 40HP Johnson Power Problem

Any ideas? Should get a couple carb repair kits and clean the carbs to see if that works?

 

[racerone]

Re: 1995 40HP Johnson Power Problem

There are no choke plates in the carburetors.-----You do not see anything moving when button for the electric primer is pushed.------Check the flywheel key as it may have sheared and that throws out the timing.-----Sounds like you should remove the carburetors for inspection and cleaning.---Look at the reed valves while carburetors are off.