1973 johnson 25 hp one cylinder not firing

[boydog40]

good spark on bottom cylinder, none on top cylinder, new external coils, pulled flywheel cleaned points, turned engine until one side pointed to "set" on the crankshaft, set it to .20 turned motor over to the other side and repeat set at .20.
what am I doing wrong?
from the back of the motor which set of points fires the top cylinder? as I see no bad/broken wires going to either set
thanks for your help

 

[racerone]

Both sets are used to fire the each cylinder I believe.----One opens and other set must be closed to direct driver coil output.

 

[flyingscott]

You may need to replace the points and condensers. Try swapping the coils around to rule out the coil.

 

[boydog40]

I have a "electrical" kit coming
I will swap the coil around tomorrow and see if it still fires
thanks

 

[F_R]

Both sets are used to fire the each cylinder I believe.----One opens and other set must be closed to direct driver coil output.

Exactly. This is a fact that many people fail to grasp. Both sets of points are closed as the magnets start their pass across the driver coil, then one set opens to fire a cylinder, but the other set remains closed in order to ground that end of the driver coil (to complete the electrical circuit). Points not making good contact are the #1 problem with these systems.

 

[boydog40]

points not making contact where? tips? or against the crank?
thanks

 

[hardwater fisherman]

I think what he was saying is that points become pitted and or dirty. You can file and clean old points. And new points will need to be cleaned . Even though they are new they should be cleaned.

 

[jimmbo]

I assume OMC went to a single coil under the flywheel system was to provide room for a charging system. It couldn't have been cost savings as there are now two external coils.
Seeing that the system is producing spark on one cylinder, I would be focusing on the coil, the wires to the coil, the plug wire and the spark plug of the dead cylinder as the culprits. Or one set of points is permanently grounded

 

[flyingscott]

There is no charging system available for the low tension magneto on those motors. The low tension magnetos are good for frying condensers which will cause a cylinder to drop. Especially aftermarket condensers.

 

[racerone]

Are you sure there is no charging system available ?

 

[F_R]

Charging system was available on the mag as used on 9.9 & 15hp.

Boydog, I was saying not making electrical contact across the points when closed. Any resistance due to dirt, grease, oil, corrosion, boogers, anything that prevents a clean metal to metal contact.

 

[flyingscott]

Are you sure there is no charging system available ?

I had a 1976 electric start 25 hp last year of the low tension magneto. I never found any type of charging system for that motor and I looked Hard for one. You may know something I don't which is entirely possible. But me not finding one was not for lack of trying and Evinrude does not list a charging system for those models.

 

[oldboat1]

Interesting thread. I didn't think there was alternator charging below 50 hp until the mid-70s -- think the generator system was still available for 40 hp motors through about '74, but don't think there was a charging system for early 25s. (May have been a lighting system, though, with a separate lighting coil for some of those motors -- and if that's accurate, seems like a rectifier could convert that to a charging system??)

Better historians than me here, so not sure.

For firing on only one cylinder, I've always thought troubleshooting was the same as other magnetos -- one set of points failing, or a bad condenser (or one of the ignition coils). With that in mind, could switch condensers around and see if that makes a difference (same with coils, as was suggested above). Should be able to seat the flywheel and give it a good spin by hand to check for spark (saves having to torque and retorque while testing).

 

[hardwater fisherman]

If you look at the parts diagrams the mag plates where the same for the 9.9/15 and the 40hp models. And they show a charge coil. I converted my 40 hp by using a parts motor I found. I know somebody with a 25hp and the we looked to see if the charge coil would fit and it did not. His flywheel had teeth for an electric start but no charging system. And also the flywheel lacked the magnets for the charge coil. He also called around and looked at salvage yards with no luck. Maybe I am wrong but he is still looking. EDIT That was only a 5amp charging system, which in my opinion is not worth paying for all the parts new. If you could find one of a parts motor than that would be okay.

 

[boydog40]

update, put in new points/condensers/new external coils/new wires/new plugs and BOOM we have fire in both cylinders! BTW yes I have teeth on my flywheel, there is also a starter bracket as well as where my "stop" button is, is also where the starter button goes (I assume!)

biggest problem I have now is I need a fuel pump (388684) and they cost almost as much than I spent on the motor!! ($150.00 for the pump)
any ideas ??? ebay has one for $104.00
just seems awful high to me, is there another number I can use?

thanks

 

[racerone]

Many fuel pumps will fit and work.----I repair fuel pumps !-----About the only thing thay can go wrong is the diaphragm.---New ones are available or I cut one to fit.

 

[boydog40]

any idea of another part number that will fit? say a 15hp pump work? bc they are like $50.00

 

[F_R]

The differences in those small square pumps is in the position of the hose nipples. The inlet one can be rotated, but the outlet is pretty well fixed. Well not really, you can change it but you have to take it apart and will need the instructions. Having said all that, the 18-7350 here at iboats will work IF--IF the direction it points does not interfere with anything. I'm not smart enough to know that.

 

[boydog40]

I ordered one just to see, I don't see where anything will hinder it
thanks for the info

 

[oldboat1]

good choice -- should work.

Sounds like you are set up to add an electric starter. It's pretty easy to rig a harness, particularly with a starter button at the motor.