1954 Evinrude 25 - Build Compression, Lose Spark

[Alex@Van's]

Hello,

I am a DC electrical parts man. We're helping a local guy get his 1954 Evinrude 25 (#25014 I believe) going. We are observing strange behavior and this forum seems to be the best place on earth to research it. I have searched the forum and did not come across this specific problem, though some threads are in the ballpark. It has stumped a seasoned small engine mechanic.

Replaced magneto cam, cam retainer, points, condensers, wires, coils, primary coil and plugs. The original cam was cracked, the retainer was broken, and the points were trashed.

If we install the lower plug, we lose spark on both cylinders. If we remove the lower plug, we get good spark up top (installed) and a spark that will jump a 1/2" gap from the lower plug.

Now here's the weirdness: if we block the lower plug hole with a finger and a little compression builds in the lower cylinder, we lose spark top and bottom. Mechanic's theory is that somehow the compression is mechanically shifting something and it is grounding or losing ground. Thinking about how this engine is assembled, I can't put my finger on any suspects. Could the crank be tilting the flywheel and moving the flywheel out of gap spec or even physically grounding to the stator?

If so, I can tell you that the parts manual for the #25014 is elusive. The mag parts were largely or all the same in the #15012-15013's but the cam bearings could be different. Part number help here would be greatly appreciated.

I am not sure if there is a "runaway" vacuum switch in this early generation. There is one diaphragm switch that doesn't change anything if it is disconnected or bypassed. The wiring is quite simple.

He has thoroughly tested everything electrically including swapping around coils, ohm measurements of all 3 coils, voltage and continuity, inspection of points for defects, and basically anything we could find in forums and videos. The no-spark does not switch to the upper cylinder after swapping any part. The only common factor is the flywheel/stator. Definitely seems to be mechanical.

I can get more info or field questions, and I have linked this thread to the mechanic, who will either send me updates/addenda to post, or create an account and post himself.

To the esteemed community, I ask: HELP?

Thanks in advance.

 

[Alex@Van's]

Thinking on this more I like the theory that the crank has slop so that the flywheel goes out of gap spec or physically contacts the stator. Has anyone seen this happen?

 

[Crosbyman]

check basics .. the plug boot to engine frame electrically goes to ground via the secondary coil winding...

measure & confirm the HV secondary ohms (4-8KOhms) with good SOLID connections and confirm that continuity is not lost at anytime. if you loose continuity while doing whatever you do then the HV circuit (s) is going open .

see if you can do testing in the dark and look for arcing anywhere .


ohm measurements of all 3 coils,
old magnetos have 2coils where is your 3rd one located ????

 

[Faztbullet]

Installing plugs or finger slows down flywheel rpm. If coils,condensers and points are good you should be able to make fire in a 1/4 turn by passing flywheel magnet past coil

 

[Crosbyman]

silly question but type of plug wire did you use.... solid strand metallic 7mm or carbon fiber wires for cars ??
to service these oldies the johson manual provides all u need for $20
Good for Johnson and cousins Evinrudes

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

 

[Alex@Van's]

THANK YOU for your advice! We will go over this and update the thread.

 

[Crosbyman]

That page is just a sample..... your model may not be so equipted in any event just disconnect the wire if you have one and that will at least let you check for sparks with no interference . the points (for testing purposes) should have 2 wires one to the condenser one to the coil primary .

Basic timing adjustments and points can be set at .020 at the maximum cam lobe position whhere the point's rub block touches the lobe

front coil is for the top plug !!
for perfect timing see video

the magneto on these oldies is quite simple in it's operation. The manual suggested covers most engine sizes in the years listed incl carbs, lower unit gear case etc...

 

[Alex@Van's]

One tweak to my description of the problem, from the mechanic:
Neither plug is installed. Each is mechanically grounded. Have spark when rotating engine. Lose spark on both when a small amount of compression is built in the lower cylinder. Does anyone have a crankcase diagram for a 25014?

 

[racerone]

There are 2 coils under the flywheel.-----What is the " primary coil " on your motor ?---The motor has 2 separate crankcases.----This issue makes no sense at all.----Many years ago I ran one of these rugged motors on an 11' class B racer.---Never an issue with spark.----Motor has been in storage for about 40 years now.

 

[Crosbyman]

One tweak to my description of the problem, from the mechanic:
Neither plug is installed. Each is mechanically grounded. Have spark when rotating engine. Lose spark on both when a small amount of compression is built in the lower cylinder. Does anyone have a crankcase diagram for a 25014?

compression has nothing to do with sparks especially if plugs are just simply grounded to the frame and not themselves subjected to extra PSI's

crankcase is just a cavity to allow movement of internal parts. ..

remove the plugs stick a screw driver in the boots and confirm sparks can actuallu jump 3/8 to 1/2 inch to the engine body... if not recheck your installation and condensers (even new ones can be bad)

 

[Alex@Van's]

I have a condenser (capacitor) tester so we can test them. The engine is not at my shop; the small engine mechanic has it, so I am working off of descriptions, diagrams, videos and images.

My understanding of the mag setup is there is a primary coil up top under the flywheel, and then a coil for each cylinder.

What I am looking for is an exploded view of the engine to identify any wear parts like bearings that could lead to excessive shaft slop. That's the tree we are barking up right now anyway.

Again, THANK YOU all for the advice. We will update this thread first part of the week.

 

[racerone]

There are 2 coils under the flywheel.-----There is no primary coil.-----This magneto is elegantly simple .---Used on motors from 1.5 to 40 HP.----Installed from 1950 to 1990 models.----You replacement ignition parts are factory original , or something else?

 

[cyclops222]

Pass on this one.
Engine designer........."I am going to make this engine confuse everyone. "
He seems like he might have.

 

[Crosbyman]

time to buy the book to understand and service your engine there are no "primary" coils under the FW ... just 2 magnets built in the FW that spin around the 2 coils .

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

 

[F_R]

I have no answer for you concerning the basic question. But there is something wrong with the information you give.
1954 25014 has only two coils under the flywheel as already stated
The 3-coils setup started in the 1970,s
The 1970's 25hp motors are totally different than the1950's 25hp motors.

I do not have the 1954 parts catalog but here is the 1955 powerhead. It is essentially the same as 1954, with one very big difference. Note that early and late production motor had different main bearings on the crankshaft. Early production was same as 1954, but later production was a catastrophe. That catastrophe resulted in total failure of the crankshaft bearings. That could go along with your suspicion concerning excessive slop in the shaft.
I'm thinking powerhead and/or other parts might have been swapped resulting in a Frankenrude motor.

BTW, broken cam is usually a result of excessive torque on the flywheel nut, spreading the flywheel taper and allowing the flywheel to sit lower on the shaft. Flywheel is ruined if that is the case. And what is a "cam retainer"?

 

[racerone]

Any pictures of this motor and the 3 coils ?----Perhaps some inventive person was trying to modernize this motor ???-----Or a newer motor with an older identification plate???