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76 jhonson 15hp no spark

Thanks tim im waiting on a carb kit to get here. if i get it running the first thing il do is a compression test. id do one now but i thought you were supposed to warm the motor up first
 
You can do a cold test, it will give us a good idea of the cylinder and ring condition.The difference between a hot and cold test is not critical in many situations. In our case here we need a "before" and "after", to see what's happening in these cylinders as the motor gets used. Sometimes after freeing up a seized motor, for instance, compression goes down hill. We will then need a teardown and overhaul before more damage is done.
 
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True, not the best numbers, however keeping in mind it is possible the rings are sticky from rust/oxidation, it is possible things could change for the better too. Maybe soak the cylinders with "P Blaster" while we wait.
 
ok il soak the cylinders with pb overnight. im going to rebuild the carb today. so im guessing this engine probably wont last if I get it going
 
well I soaked the cylinders overnight the results are not good. top cylinder 105 bottom 75 to 80. should I even try to start this engine or is it done.
 
We try to teach but ?------Start it up and run it.------It may run real nice for years.-------It may come to a dynamic halt after one hr.------You will have learned a lot.
 
lol im glad I tore into it and just from.this thread and tim ive learned alot. I kind of figured it would turn out this way. so I guess il put it together and hope for the best.
 
well I found a 1974 15hp on craigslist for 300.00 guy says it runs good. If that motor is in good shape will probably keep the 75 as a parts motor
 
These are among the best lightweight and fishing outboards ever made. You throw them on your shoulder and carry across a 1/2 mile portage. Today that is impossible as 15 horse motors can be both bulky and heavy. If I had to choose one motor to live and die with, out in the bush wilderness, it would be one of these. Collect them and treasure them, brother. You can trust your life to them........and I HAVE!

When you go to buy that motor, be sure to bring your compression gauge. I always do, even right in the pawn shop. If he won't let me test it, I try to get it super cheap. If that won't work, I go shopping somewhere else.
 
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15 johnson powerhead 3-21-16 003.jpg15 johnson 1974 3-28-16 003.jpgWhen I find a nice clean one, tune it up, maybe even touch up the paint in base/clear, supply a reconditioned base/clear finished OEM steel tank with a one year warranty, I sell 'em for 850 to 1300 bucks. That's the truth, brother. I have paid even 750 for them and still made a handsome profit. Fantastic motors. This is the one I sold for 1300. You can see where I masked off the area around the idle speed decal, but forgot to take off the tape before the epoxy clear coat. Look how nice that epoxy brings the finish back to life. Here is the original powerhead but simply repainted in base/clear epoxy. It was NOT rebuilt, didn't need to be, compression 110/110.
 
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wow thats good if this one im going to look at has good compression. il probably pick it up since i can get it for 300.00. All ive ever ran on my boats is 77 up to late 80s jhonsons I like them. never dealt with points motors til now always coil pack motors.
 
For the record, I have NEVER been stranded with a "points" motor. Worst case scenario, you drop one cylinder, get back to camp. When a pack fails.........NO warning, and they have failed on me on more than 1 occasion. You break out the paddle. In my case I generally run twin 15's, so a dead pack is no big deal.
 
I have also been stranded by a bad pack. but how would the points get you home when the pack wouldn't. im curious that way if I get a points motor and it happens i know what to do
 
A points motor will drop only one cylinder because the system uses independent components. You can almost always get back to shore or back to camp on one cylinder. I operate 2 remote camps in NW Ontario. As time goes on, I entertain fewer and fewer guests, however, over the years I have focused on the most reliable equipment available. With electronic ignition, I most often run twin motors. The 15's are lightweight and side by side can get a nice load up on step.
 
Well not really true !!------The points motors with the UNIVERSAL magneto had 2 completely seperate ignition systems .----One could fail and you limp home on the other cylinder.------The 76 15 HP models use one driver coil and if that fails both cylinders lose spark !
 
Yup, thanks for the correction and clarification, Racer. The 76 was the "hybrid" so to speak. That driver coil was pretty reliable, however. I never remember a sudden failure with one, at least not like what can happen with a pack.
 
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the engine started on the 8th pull and actually ran pretty good.
but it leaks fuel where you plug it in. the ends are new and the fuel line is new. The fuel line does fine on another motor. im wondering if the end on the motor is no good.
 
Yes, I have seen them get pitted and deteriorate. Look closely at the plating on it to see if there are any defects.
 
I was happy too see the motor run it actually runs pretty good. now I know it may not last long but it started up quickly.
 
Somehow I had a good feeling that it would turn out okay. Your intentions were genuine. You should try another compression test after a run or two and report your findings. They may actually go up. See back to post #5. Good job.
 
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Thank you for all the help I intend to do another compression test after ive ran it a couple times. I bought another 74 15hp it looks great both cylinders have 100lbs compression. It starts and runs but doesn't want idle but the previous owner left gas in it. so im going to clean the carb and see wh

t happens
 
Sounds like a great buy....$300.....WOW! Might have used ethanol? No matter what I preach, it seems about 1/2 of my customers are ignorant to the damage that ethanol will cause to rubber, certain plastics, as well as simple fuel degradation resulting in octane fluctuation and ultimately damaging corrosive deposits. A problem with ethanol that it actually "invites moisture". This makes it a problem in marine environments as well as aviation, "where it is actually illegal to use". If your plane goes down the FAA will conduct a fuel test, if alcohol is found, you will be in trouble......I know as I am a pilot. Diesel fuels today are also oxygenated. They have about a 2 year shelf or storage life. I use heating oil in my equipment with an Amsoil additive. Some of my fuel is over 30 years old and still very effective. In fact this past winter, I plowed with my 1976 580 Case at temperatures to -30F.
Ethanol will suspend its own weight in water, so as it carries that water, it will separate and settle to the tank bottom. This creates also another problem in that the ethanol is expected to provide octane and when the petrol floats up to the top, we have the octane separation. Once apart these two fluids cannot remix. Modern electronics will sense problems with detonation and adjust timing and mixture to the best of its ability. Other equipment with static mixture and timing will run improperly and can cause engine damage. By using pure petrol at 90 octane, we ensure reliability and performance for many years in our older outboards, small engines, seasonal equipment and vintage autos.
 
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I agree completely on the ethanol. none of my small engines get ethanol fuel. I took the carb apart and it was obvious it had sat with fuel so im waiting on a kit to get here. Il try to post some pics of the motor it is very clean for the year
 
outback32 said:
the engine started on the 8th pull and actually ran pretty good.
but it leaks fuel where you plug it in. the ends are new and the fuel line is new. The fuel line does fine on another motor. im wondering if the end on the motor is no good.
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The problem kind has to be with the end on the motor. That part is fairly easy to replace and I imagine readily available from most outboard dealers. Even easier to replace for a guy who already owns a 1976 15Hp motor that he does not have much use for.
 
Good, see post #53. I have several extras around here. They can get wear on the male fitting. I always recommend removing the coupling when trailering your boat. Road vibration, dust, etc. can beat it up over time. I have a tube/cover that is tied to the motor to put over that pin so it's always covered when the boat is in transport. Don't need dirt and dust to get on it.
 
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