1973 25hp Evinrude

[Arkansas Traveler 64]

First time posting, however I wanted to thank everyone for the wealth of information that is available on these forums. I have a fairly new to me 1973 25hp Evinrude Model 25302A. My knowledge is limited as far as working on outboards. I have purchased the manual that accompanies this motor. Motor would start right up but i had what seemed as a misfire on the bottom cylinder. Started it at home in a barrel all seemed well. Took it to the lake and it would hesitate upon acceleration and seemed the 2nd cylinder would kick in about 1/4 to 1/2 full throttle. I confirmed that this cylinder was not firing by pulling the top plug wire and the motor would die. I found i had a very weak spark on that cylinder. When i purchased the motor the previous owner did a compression check in front of me and they were 124 top cylinder and 121 bottom cylinder. I pulled the flywheel and was able to clean/adjust the points so that i had a strong spark on both cylinders. The spark would jump 7/16 on the spark gap tester for both cylinders. When i reassembled everything the pull rope seemed to have alot more resistance than it previously had before i reset the gap on the points. I took everything back apart and did not notice or hear anything that could be catching on the flywheel. Reassembled and started the motor. Fired right up on the first pull but seemed to be idling extremely fast. I shut the motor down adjusted the low speed setting on the carb and attempted to restart the motor. It started to fire up but i heard a pop what sounded like under the flywheel and that was it. It will not start now. I still have spark on both cylinders but it seems to be much weaker only jumping about 1/4. There seems to be to much resistance when i attempt to pull start the motor with spark plugs in. With the spark plugs out it feels normal. Sorry for the long post but tried to give all the details that might be needed. If anyone has any idea where i might start to track this down would be really helpful. Thank you!

 

[F_R]

I could make a bunch of guesses, but that's what they would be. Nothing in your saga jumps out at me.

 

[Arkansas Traveler 64]

At this point I am good with guesses. It will at least give me something to start checking. I have looked over everything i can see and nothing is jumping out at me. Have looked extensively at past posts trying to find someone with a similar problem but have been unsuccessful up to this point. I am planning to go and purchase a compression tester tonight, but am unsure if i can even get a good reading. What would normally cause the flywheel to be hard to turn with the plugs in but not out? I figured since i noticed the hard pull start first (prior to it starting and running) it might be a good place to start.

 

[JJsays77]

I have a guess because this happened to me a couple weeks ago. You might have the spark plug wires crossed!

 

[F_R]

That's what confuses me. One would think that whatever it is would affect it at least to some degree with the plugs out. I'm thinking a trashed roller bearing, but that is way out in left field.

 

[oldboat1]

The low speed needle on the carb is a mixture adjustment -- not to be confused with a throttle adjustment. BUT if you adjust the needle clockwise (leaner -- more air, less fuel), the engine rpms will increase, similar to throttling up. It sounds to me like you set it too lean and got a lean sneeze (a pop), and it's now too lean to start. You should probably start over with the needle adjustment. Set it 1 to 1 1/2 turns out from lightly seated, and see if the engine will start. If so, let it idle at whatever speed it runs smoothly, then readjust setting after it warms up.

It wouldn't hurt to check the assemblies under the flywheel. In particular, make sure the coils are exactly in place -- perfectly flush with the machined edges at the mounts (and tightly screwed down). As a final check, I would turn the flywheel by hand (clockwise) and feel for any binding. (Pull off the plug wires before doing that or the engine might fire.) Binding would exist with plugs in or out, but maybe you are just feeling compression.

I'll guess you probably have a carb adjustment issue.

 

[Arkansas Traveler 64]

Thank you for the replies! Double checked the spark plug wires all was good there. I had labeled them prior to disconnecting just to be safe. I went back to the basics and followed the advice of setting the needle adjustment back to 1 1/2 turns out. Guess it could of been a lean sneeze as i had not experienced that yet. It did not sound like metal on metal. Also went back under the flywheel and double checked everything/ reset the points. What would have caused the points to be out of adjustment already? I was still getting spark prior to readjusting just was a very weak spark. I am back to decent spark (not quite the 7/16 but definitely over 1/4) on both cylinders and was able to start the motor again. It would not run on either cylinder by itself this time. Still seemed to have more resistance than when i started all of this. After letting it idle for about 5 minutes, i noticed that i had oil in my test tank so will need to drop the lower unit now to see what is going on. This was not present before or while i had it out on the lake. I will drop the lower unit and see if something went astray with the water pump/impeller. I still had water being discharged but am wondering if that is were the extra resistance is coming from. I had changed the lower unit oil when i first acquired the motor and did not see any water or metal shavings in it. It doesn't really feel like there is much resistance with the spark plugs out but maybe there is more than there should be. I had never really turned the flywheel without the plugs in prior to starting this. My only base point was that it increased while plugs are in. Thanks again, I will post my results after i am able to remove the lower unit tonight.

 

[oldboat1]

When you fiddle with carb adjustments (i.e., as you fine tune the thing), there will be a bunch of exhaust stuff in your barrel. If the ignition is working right and the carb is adjusted correctly, the motor will begin to run cleaner -- but it is what it is. Need to get out and run it to get it in the best condition.

The impeller provides some resistance, and I guess you might feel that turning the flywheel by hand with the plugs out. If you remove the l.u. and immerse it in a tub, you can feel impeller resistance by turning the driveshaft (always clockwise). And you can test the pumping function by spinning the shaft with a drill while the lower unit is submersed.

You can also pressure and vacuum test it yourself, or take it to a shop for that. If you drain a little of the oil and it is clear (not milky), I would be inclined to just run it -- check condition of the oil again after running. It doesn't hurt to check your work, of course, but chances are it's working fine.

Operating temps are important, so will want to confirm it's not overheating (if the top of the head is too hot to touch, it's running too hot.) If you like metrics, get an infrared gun and check temps -- should run somewhere in the range of 120 to 140F. Over 160F is too hot.

Just a learning curve. Will get a handle on what's concerning and what isn't as you play with it.