1976 Johnson 15hp no sign of wanting to start

[UnDeRFLiP]

Any chance you have the spark plug wires switched?

Definitely not. I'd be kicking myself if that was the case, haha.

 

[UnDeRFLiP]

So, a little update. I still don't have the engine running. I replaced the points with brand new and also replaced one ignition coil since it was producing weak spark. I now have strong blue spark jumping 7/16" on every pull but the engine still won't start. The plugs seem to be dry... I can smell gas on them but they look dry as a bone. It seems there isn't any fuel getting to the cylinders. I've rebuilt the carb 3 times now so I know it's not the carb.

This engine was sitting in a shed for 4+ years unused after not being taken care of... is there any chance the leaf valves could be rusted/corroded shut? I'm a little stumped at this point aside from tearing the entire thing apart and essentially rebuilding.

Any ideas? Thanks!

 

[Tim Frank]

Any ideas? Thanks!

Yes. Pay closer attention to the advice you are getting.

Simplified ...... you need compression, ignition, and fuel for that motor to run. You appear to have the first two.
At least 3 posters have suggested how to ID a fuel problem....e,g. posts 11 and 17.

Also, a great suggestion was to verify that your choke is functioning properly or you will be straining your arm with little hope of success.

 

[UnDeRFLiP]

Yes. Pay closer attention to the advice you are getting.

Simplified ...... you need compression, ignition, and fuel for that motor to run. You appear to have the first two.
At least 3 posters have suggested how to ID a fuel problem....e,g. posts 11 and 17.

Also, a great suggestion was to verify that your choke is functioning properly or you will be straining your arm with little hope of success.

Thanks.

I've done all the mentioned tests (squirting pre mix in to the cylinders, choke is functioning properly) and still nothing but a cough or fart at best.

With the choke closed, after a few pulls there is gas dripping out of the front of the breather so there is vacuum pulling gas out of the float bowl in to the throttle body. It just doesn't seem to be getting from the carb to the cylinders. There is also a bit of an oil slick in the water after a handful of pulls and if I pull up and lock the motor at full tilt fuel spills in to the water as well.

 

[Tim Frank]

Are you squirting the premix into the carb throat or into the spark plug holes?

 

[UnDeRFLiP]

Are you squirting the premix into the carb throat or into the spark plug holes?

In to the spark plug holes.

 

[oldboat1]

Assuming the idle circuit is squeaky clean, the needle initial setting is 1 1/2 open (c.clockwise) from lightly closed. The engine should start at that setting. Make adjustments from there (gradually lean it out (clockwise) until it quits or lean sneezes, then open about 1/4 turn.

If push comes to shove, a shot of the much despised starter fluid in each cylinder may wake it up. Water in your test barrel should be about half way up the leg.

 

[Tim Frank]

Try a small spray bottle of pre-mix and mist a few shots directly into carb throat.

When you did the carbs, did you remove the welch plugs and get the idle passages spotless?

 

[Tim Frank]

Yes. Pay closer attention to the advice you are getting.

blah....blah...blah....

And yes, the choke is functioning properly and I have also tried a little gas in each cylinder hole.

The best I am getting at this point is the odd "cough" with a small puff of exhaust coming out.

Someone needs to pay closer attention to the posts....and it is not you.... :facepalm:

Missed your confirmation that you had tried those suggestions. My apologies....:embarassed:

 

[UnDeRFLiP]

Try a small spray bottle of pre-mix and mist a few shots directly into carb throat.

When you did the carbs, did you remove the welch plugs and get the idle passages spotless?

I did not remove the welch plugs when I did the carb... From all the reading I did, it never seemed to be a stressed issue. I guess I should try this. If you wouldn't mind, can you explain what removing the welch plugs will accomplish? I've tried to search for a cutout diagram of this specific carb to see where each passage goes, but no luck.

 

[Tim Frank]

Most times there is nothing wrong behind those plugs, but they usually are the access to clean the idle passages.
It is simply sensible practice since it is quick and easy.
The one time that you omit this and it actually is truly needed, as you dig in to pull the carb again and dismantle, you'll wish you had done it when you had the carb off.

BUT....if you have tried adding some premix through the carb throat with no luck, that is a concern.

I know you are certain that the plug wires are not reversed, but just for giggles maybe switch them for a few pulls.
I cannot speak for anyone else, but i have certainly done dumber things than that over the years.

 

[OptsyEagle]

I was just going to suggest that. If your compression is OK, you have spark and you put fuel in the cylinders and it still will not fire then it has to be timing. Either your coil wires are reversed or your point gap is incorrect or your flywheel key is sheered or not there...or both spark plugs are fouled (which I think you changed but can't remember now).

Maybe someone else knows some other things that would keep that motor from starting but I don't. I would think if your leaf valves were corroded, you would get a few pa pumps out of it, when you added fuel to the cylinders, and since you have leafs on both cylinders I doubt both would fail at the same time. Remember these motors will run remarkably well on only one cylinder, but just with significantly less power at the top end.

It sure sounds like a spark problem to me, either the spark itself, spark timing or bad spark plugs and with that being said, I doubt it is point gap because I think I had a gap of less then .003" once and that cylinder was still firing, although I obviously was not getting all the work out of it as I could. The other point was around 0,014" if I recall so it probably masked a lot of the deficiency. I just mention it to get you to reverse those coil wires again and give it a try. If they are reversed you are sparking at "bottom" dead center on both cylinders and as you know that will never work.

 

[thatone123]

These are legendary outboards and I have seen them run when logic and reason sez they should not. I bet it is one of the coils. Do not be afraid to use a little starting fluid. I know some will say no no, But I have used it on dozens of engines with no ill effects. Just a small spray. Will start it when nothing else will. Sounds like the electric ignition system. I actually find that the old mag engines start better than many newer CDI units when properly set and tuned.

 

[Tim Frank]

These are legendary outboards and I have seen them run when logic and reason sez they should not. I bet it is one of the coils. .

If he has a spark jumping a 7/16" gap, his coils are fine.

,..... a little update. I still don't have the engine running. I replaced the points with brand new and also replaced one ignition coil since it was producing weak spark. I now have strong blue spark jumping 7/16" on every pull but the engine still won't start. ...............

Do not be afraid to use a little starting fluid. I know some will say no no, But I have used it on dozens of engines with no ill effects. Just a small spray. Will start it when nothing else will. Sounds like the electric ignition system. .

He needs to get it running on gasoline....not ether....

 

[oldboat1]

Appropriate plug gap?

 

[flyingscott]

Are the points going .to the correct coils? Have you tried switching the spark plug wires? Have you checked the flywheel key? Anyone who tells you the 74-76 9.9/15 hp motors are legendary is partly true. They have legendary bad ignition systems, gearcase problems and idling problems. The 77 and later.motors are much much better.