Help with 1973 18hp Evinrude model 18304 A

[Kawaiikeno]

I've ran into something I haven't seen before where a timing light will work on one cylinder but not the other when it does in fact have spark.
Ignition system has a single charge coil with two sets of points and condensers feeding two separate coils. I have cleaned and checked all the grounds cleaned all mating surfaces checked all the connections.
Bottom cylinder lights the craftsman automotive style timing with adjustable advance it has a battery red positive and a battery black negative and an inductive pickup for the plug wire.
Engine runs fine( I have added electric start)
Thanks Mike

 

[racerone]

Clean breaker points again.

 

[Kawaiikeno]

I was wrong about it having spark I tested it in the shop and it did, then moved it outside to the test tank to check timing.
I have no spark on the top cylinder after swapping the coils still nothing on the top. I had a spare driver coil that I thought was good and tried that but still nothing on the top cylinder.
Not sure it's a valid test or not but I bypassed the points and tested the output from the leads I get 6v on the bottom and less than 1v on the top on both driver coils
Thanks Mike

 

[racerone]

The DRIVER coil is the one under the flywheel.----Make sure both sets of breaker points are absolutely clean.

 

[Kawaiikeno]

So this is the second driver coil that has lost the top cylinder in 2 years.
I've taken the plate off and inspected everything wires are all good with no signs of being pinched.
I'm thinking of running new wires just to be sure. Also last year I did loose the top cylinder but found the condenser was bad and changed it and all seemed to be good.

 

[racerone]

??----The driver coil under the flywheel is used to fire both coils.-----More trouble shooting is required.

 

[Kawaiikeno]

So far I've done 15 of the older Evinrudes 1954 up and this was one of the first ones I did, also one of the newest with the difference being the driver coil powering the two separate coils.
I do have all the parts on hand to convert it back to the 2 coils under the flywheel

 

[Kawaiikeno]

Yes I know that the driver coil is the one under the flywheel.
The no spark issue follows the wires coming from under the flywheel I have swapped the condenser again and the points I have tested both leads with an ohm meter and they both are almost the same. that leaves the driver coil I just can't figure out why it's going bad. I tested it by the book as I understand it,(by connecting each of the 2 leads to an Ohm meter) The latest driver coil tests at 1. Ohm and the one I had saved tests at .9 the 1973 Evinrude service manual lists the spec at .8 +- .05 so both show out of spec.
Thanks Mike

 

[racerone]

I am quite familiar with these motors.----But I can not do the trouble shooting from 999 miles away.

 

[Kawaiikeno]

LOL I realize that, if it were an easy one I wouldn't be looking for ideas.
I've learned a few hard lessons along the way one of witch is don't mount the ground lead on a CDI box to the same bolt that mounts the CDI box to the engine (the black washers under the CDI box are actually Plastic and you won't get a ground from it and no spark). Also don't buy anything larger than a 15Hp without electric start as the starter and bracket sell for more than the motors and are a bear to pull start!
I have a new driver coil and oem points and condensers on the way so I'll try that.
Thanks Mike

 

[jimmbo]

One of Magnets in the Flywheel hasn't given up the Ghost has it?
Any history on this Motor?
This is a Long shot, but, is it the correct Flywheel for that Motor?

 

[racerone]

Correct with that ignition you need 2 magnets.-----At 180 degrees apart.

 

[Kawaiikeno]

History is I bought the motor in 2020 as a non running pull start only average condition for the age complete motor. Compression was 120psi on each cylinder with no spark on the top cylinder I ended up going completely through it replacing anything that even hinted at being questionable.
I replaced all the seals in the lower unit, top and bottom crank seals, all gaskets, cleaned the carburetor, top coil was bad also the charge coil was replaced, points and condensers, also electric start was added with a new starter ( I did use a regular small engine solenoid)?? with a simple water proof start and stop buttons added to lower cowling.
I used it as my primary motor all of 2020 and 2021 late in 2021 I was fishing and it started acting up and quitting about a minute later fouling out plugs.
In the test tank with new plugs it would run on both cylinders for a few minutes then drop the top then foul bottom and quit. After much head scratching I found the top condenser felt waxy to the touch, I replaced it and all was well until 100 miles of Canadian dirt roads loosened up the thermostat housing on start up it ran fine for about 2 minutes then quit, after removing cowling I found it was spraying water all over the inside.
I put on a spare Honda 4 stroke 7.5hp and fished the week.
I do know that the points and condensers were china crap I'm not sure on the charge coil.
I have since purchased a genuine oem charge coil and condensers the points I have coming are sierra brand.
The issue I have with the ignition is I don't understand how it reverses polarity and how a marine starter solenoid can work without a ground
Thanks Mike

 

[jimmbo]

One of the Flywheel Magnets is North, the other South, that is the Polarity change

 

[Kawaiikeno]

I don't have a scientific way other than the screw driver test but they both
( actually 4) feel the same strength.
The new driver coil and condensers came yesterday while I was away fishing and it also tested at 1.0 Ohm so I didn't have much faith that it would cure the problem as spec is .85 +-.05 , but I now have good spark on both cylinders.
It's plain to see I have no idea how to test driver coils even after reading the service manual something I'll have to work on.
now for the test tank and timing check
Thanks Mike

 

[Kawaiikeno]

One of the Flywheel Magnets is North, the other South, that is the Polarity change

I read that,but does that also change the that spark on that cylinder from negative ground to positive ground?
Thanks Mike

 

[F_R]

I read that,but does that also change the that spark on that cylinder from negative ground to positive ground?
Thanks Mike

Interesting question. I don't think it does because there are two sets of magnets 180 degrees apart. But I could be mistaken. Issue has never come up in my experience anyhow.

BTW, do you know that the early OMV v-4 magnetos produced two negative sparks and two positive sparks per revolution? They run fine anyhow.

 

[Kawaiikeno]

Interesting question. I don't think it does because there are two sets of magnets 180 degrees apart. But I could be mistaken. Issue has never come up in my experience anyhow.

BTW, do you know that the early OMV v-4 magnetos produced two negative sparks and two positive sparks per revolution? They run fine anyhow.

No I didn't know that.
Only reason I ask that is I'm also finishing up a 1969 25hp that started out as an electric start long shaft motor that didn't have spark on one cylinder, The previous owner had ran a jumper from the solenoid to ground to get the solenoid to work. If I removed the jumper it had spark on both cylinders but the solenoid wouldn't work so I replaced the solenoid with a grounded type and all is well.
Except it will idle down for a little while then just quit hit the start button and with no other input it will fire back up and run perfect till it does it again which could be just a few or 20 minutes
Thanks Mike

 

[Kawaiikeno]

Seems to be running like it should after replacing the charge coil under the flywheel even though the new coil tested the same as the old it now has spark on both cylinders
Thanks to all who replied
Mike