1973 evinrude 25hp wont idle

[brsoo]

Just wanted to post my results. This motor has been pretty hard to figure out and I'm possibly still working on it.
I started it almost immediately the very first time I hooked a tank to it. But it would only run at wot with no choke. If I tried to bring it down it would cough and misfire? Then die out. I happened to also have a johnson 71 25hp so I figured they where almost the same motor. I rebuilt my one carb with parts from both to use the best parts.
Then I rebuilt the fuel pump
It still didn't run.
I then re gapped the points and plugs.
Still didn't run.
After a LOT of research I decided maybe I was mixing the wrong parts. And maybe I had a weak spark? (Initial problem)
I found one person suggest the spark being stronger removed from the cylinder. So I put old plugs in the block with new ones grounded. It did show a weak spark!
So this was my fix...
New condensers
Cleaned and set points.
Flywheel was not tight enough.
Spark plug wires where loose.
They where not pushed into coil far enough
New plug wires. Stripped like speaker wire to create stronger contact!
Tested jumped 1/4 inch.
Carb rebuild kit.
Later found fuel pumps where not interchangeable.



In short.
Do not mix parts until you rule out the issue.
Check for weak spark with a tester.
Don't try to rebuild a fuel pump of these years
Buy a carb kit.

I think I had weak spark and that's why it ran funny.
Then after fixing the spark I found I changed too many parts. Turned out the fuel pump I changed out wasn't the same and changed the ratio.

I hope this helps someone in the future and sorry for rambling. Just trying to help others!
I was pulling my hair out on this...

If you have anything similar feel free to ask!
I now know my motor pretty well!

 

[brsoo]

This is my motor. It has a driver coil and two ignition coils. I haven't seen much talk on this style. It was hard to find any info on how to test the ignition system on this style..
The fuel pump pictured is the one that would not work on mine. Mine was flat underneath as apposed to raised.

 

[brsoo]

Is this normal idle for this motor? I think the rpms seem high and it's just loud! Shifts good. Ill test on boat soon

 

[brsoo]

PLEASE HELP!
Took the boat out today and it ran AWFUL. It started after 5 or so pulls then wouldn't idle very low. Let it warm up. Then set out. It only went about 5mph just faster than kayaking speed.
Besides my issues. Are there standard items that break more often on these motors? Is like to just replace parts that normally fail. I want it to be dependable

 

[Bosunsmate]

Have you done a compression test? Have you tried a drop test? (pulling one spark plug wire off using insulated pliers to see if that cylinder is working) is the engine doesnt change rpm when you pull it off then that cylinder is dead)

 

[wauto]

Remove the flywheel and check your stator plate for wobble. My 73 18hp stator plate would rock back and forth at least .020, raising havoc with the points.

 

[brsoo]

I did notice the armature plate to move back and forth about a cm. I was wondering if that was the problem with the idle randomly changing.
How did you fix this?
Its is spewing sludge from the lower that I will rebuild soon. Could this make it bog down??
To bosunsmate, I did a compression test. 120psi per cylinder. I have not tried to pull a plug as it runs. How would it run with out a cylinder? Or have good compression? Maybe ill check it again... Seems good tho

 

[brsoo]

[No message]

 

[brsoo]

No Title

I assume this is the lower unit spewing gear oil. I changed it and it looked good! Black and smelly but no water. I assume that normal and old. I have new seals in the mail I will rebuild it..

 

[hardwater fisherman]

I think when he said check the mag plate he meant up and down movement. While running if wobbling then this can through off the spark.

 

[brsoo]

Thanks for the responses. It doesn't seem to have up and down movement. Its a little loose feeling side to side..

 

[Bosunsmate]

This is how it could run on one cylinder:
"Took the boat out today and it ran AWFUL. It started after 5 or so pulls then wouldn't idle very low. Let it warm up. Then set out. It only went about 5mph just faster than kayaking speed."

 

[brsoo]

I get where your coming from. Obviously the lower isn't helping. But I too think its something more?
I will do another spark test. I did try to put the hood back on and it moved the spark plugs maybe I had weak spark after moving them....
Thanks again. That helps me diagnose it

 

[Bosunsmate]

Make sure the spark jumps a 7/16 gap
You should also check while you a at it that when the flywheel is at 0 That the top cylinder is at Top Dead Centre

 

[brsoo]

Hmm I can now check the gap with my checker. I've been checking 1/4 gap and its been ok. If it doesn't jump what should o change? A coil???
How do I check that flywheel is center??

Is this a timing check?? Thanks!
I'm going to start digging tomorrow!
Will gas eat my impeller? Idk how else to clean this sludge from my lower unit chambers with out gas...
Was going to open the thermostat and pour something into it to start....

 

[wauto]

PM'd ya

 

[Bosunsmate]

Hmm I can now check the gap with my checker. I've been checking 1/4 gap and its been ok. If it doesn't jump what should o change? A coil???
How do I check that flywheel is center??

Is this a timing check?? Thanks!
I'm going to start digging tomorrow!
Will gas eat my impeller? Idk how else to clean this sludge from my lower unit chambers with out gas...
Was going to open the thermostat and pour something into it to start....

Dont change a thing until you a sure, it could be anything from sparkplug up stream
Flywheel should have numbers on it, these a your timing marks. FInd the 0 on it and line that up with a pointer on your engine that you should see somewhere just outside the flywheel. At this point the top cylinder should have its piston at its maximum travel up the cylinder, ie the highest point of compression. Yes this is first main part of checking timing
Depends how good your impeller is, it hould be ok if you dont take too long, but that is only an opinion. DOnt fiddle with thermostat unless you really want too

 

[Bosunsmate]

PM'd ya

If that was me it hasnt turned up. Not sure i get them anyhow.

 

[brsoo]

So should I check the 7/16 spark gap with the plugs in the block or out? I've been checking with them in..

 

[brsoo]

Bosunsmate
So I couldn't find a 7/16 but set it just under 1/2 and there was no spark. I left the plugs out and had lower unit out so it was realllly easy to pull.
I cleaned and set my points and tested my two ignition coils and got 4500ohm on both. The driver coil I do not know how to test. The only two wires coming out bury the needle. Trying to test the body as a ground has no continuity.
Idk if I'm correctly testing these coils.