1972 Johnson 25 hp, elec start... back from the dead!

[RandyJ]

I acquired this motor a couple of months ago, no fire, sat up a few years. To get it firing I replaced one coil and both condensers, cleaned and set the points.020. Without touching the carburetor it cranked and ran good out of the water. I put it on a small boat today and it did kind of okay when I idled out. Once I got in the open I throttled up. It slowly increased rpm but tended to sputter. The more I ran it the better it got up to a point. Then like magic it would sputter some then take off and ran fantastic for maybe 100 yards to 1/4 mile..then act like it was only hitting on one cylinder. I tore it back down to find a plug wire loosely fitting in one coil. While I had it down I went through the carburetor...spotless! The guy I got it from had the carb cleaned before putting in storage years ago. I did the ritual cleaning of everything in the carb and reassembled. Now it's a little hard to crank, still sputters and from the looks of the exhaust is running extremely rich with black oily gas/carbon coming out the exhaust. I can't tell if it's just not always firing or if it is flooding causing it not to fire. Just need a little help thinking on this ....

 

[Daviet]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Use a timing light to check the spark and see if you are dropping a cylinder. Sounds like you caused more problems by overhauling the carb, might need to revisit the carb and double check everything. Did you remove the core plug on top of the carb and clean the low speed passages in there? Float level set properly?

 

[CatfishMN]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

My 2 cents is to check the carb float and the needle. Seems almost like you may be flooding out one cylinder.

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

no welch plugs to replace the old ones with... just removed all that I could, sprayed really good with carb cleaner, cleaned all the holes I could get to with welding tip cleaner, tooth pics and Q-tips. At first I couldn't get it to start at all then when it did it ran wild until I got my wits about me (3 to 5 seconds). I blew everything dry and clean with air.... hooked to my compressor, not some sissy canned air. The only thing I did notice is that the rubber tip on the needle has a typical ring around it as old ones will have. Both spark plugs appear to be firing well. I've had jet skis do this but after running a while they tend to clear up and run better which I pretty much credit to the running cleaning the spark plugs and freeing up trash in the carbs as well as drying out moisture in the electronics.

 

[AlTn]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

recently rebuilt a '71 25 hp. carb...it had been sitting long enough for the gas to evaporate and leave a tar like substance in the lower float bowl...so tarry in fact, I had to pull the needle out of the seat with some pliers..anyway...the new kit had an all metal needle, no rubber tip, the last 3 carbs I've rebuilt with brp kits have had all metal needles.. you may have to kit your carb and remove the main jet for proper cleaning...I let this one soak in chemtool carb cleaner for ~ 6 hrs...after rebuild it started up quickly and runs well...kit was ~ $30 and included a new float

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

thanks... I might happen to have a kit in the shed out back... maybe even a needle too.

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Okay... did everything except take out welch plugs. I cleaned thoroughly with carb cleaner, pipe cleaners, blew out everything really good with air hose. A few years ago I had a 20 hp Johnson, 1971, that acted very similar. After I finally trashed it I tore the ignition plate off to find a pinched kill wire on one side.
Today I tinkered with this thing endlessly with some improvement but still far from right. I've gone through the carb 3 times and am quite convinced it is thoroughly clean... removed high speed jet and cleaned extra good. All gaskets, new needle & seat. It smokes a good bit when I first crank it up. I run out to the main part of lake before it begins to hit on both cylinders but it idles very good and has good slow speed eventhough it seems to not be hitting on both cylinders. I replaced plug wires, no change. I've completely removed kill wires, adjusted points AGAIN. The hose from bottom to top of crank case was leaking at the top so I fixed that problem. I found a bolt missing on the water jacked cover, replaced that and tightened all other bolts in that cover. It runs like it is bogged down then will blast off and may or may not stay running on both cylinders. For some reason, I just keep thinking it's an electrical problem. I've put clean plugs in and checked for .030 gap. Points at .020. When it is running right it runs strong and very smooth and does not get very hot. The top plug will burn your fingers but the bottom is cool enough you can pretty much keep your finger on it. Water jacket is just good and really warm. I will do the timing light check now that it's dark outside and I won't have problems seeing the light... but just doing a spark check I'm seeing good spark on both plug wires. No high speed adjustment on this motor so that's one thing I can't change.

 

[Daviet]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Just another thought, does your fuel pump mount on the lower cylinder bypass cover? Have you checked the fuel pump to see if it might be leaking fuel into the lower cylinder?

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Yes, it does mount on the lower cylinder... what's a bypass cover? No problem to check... sitting in front door now... I can tell you that the fuel pump is pumping very well, does not leak on the outside and the screen is clean.

 

[Daviet]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Yea, but is it leaking into the cylinder, you can't see the leak with the fuel pump mounted. If you have a leak it could flood the lower cylinder at lower speeds and then clean itself out at higher speeds. Just a thought.

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

Thanks for at least thinking! Here's a pic taken with my cell cam and a flashlight...

I may have narrowed the problem down. It appears to have intermittent firing (as I have been guessing). When it does fire it is a strong blue spark. I don't have a fancy spark checker so just took a brand new plug that I don't have a clue what it fits but it has a long center electrode. I straightened out the ground electrode to get at least a 1/4" gap. I checked top cylinder and bottom. Actually, I left the top plug wire on and it started and ran pretty dang good on that one cylinder. When I put a regular old dirty plug on the top wire and the spark checker on the bottom wire the top plug wire was firing several times more than the bottom wire. I'm beginning to believe it is possibly a bad condenser unless there is something close or a bad connection in the ignition, frayed or skinned wire. Other than just swapping parts I'm not sure how to isolate the problem tho' one condenser may be suspect since the top appears unusual like it's not sealed good in one place at the edge. Too bad I can't see what's going on under the flywheel with it running.

BTW... I checked for the pump leak by unscrewing it from the mount to the block cover thingy then pumped up the fuel with primer bulb... no sign of leak.

 

[RandyJ]

Re: 1972 Johnson 25 hp, elec start... back from the dead!

I THINK IF FIXED IT!.... will have to put in the water tomorrow morning to find out for sure... I swapped condensers (used an old one) for the lower cylinder. Of course, when I started all this I checked for strong blue spark. When I used the spark plug with the tip bent back I discovered that it is blue but doesn't spark nowhere near as good or as often as the top cylinder. So, since I've already changed plug wires it pretty much had to be either a condenser or coil unless there was a short. I was able to start and run the motor with the top plug wire disconnected/grounded. It would not do that before but would start and run on the top cylinder. Sounds stronger & smoother now.

If it runs out good in the morning I'll be a very happy camper! This old man is tired of pulling a starter rope and needs an electric start motor so I can go fishing! I'm too tight and too broke to pay good money for a new motor at todays prices and this one seems like a nice old one with plenty of life left in it. Next item is to figure out why it had water in the lower unit when I got it.... so far I suspect drain/vent screws since neither had a seal/gasket. I sure hope that's all there is to it....