1974 25 hp Evinrude with a couple issues

[kos]

I have had a few issues with this motor lately that I am trying to diagnose. It seemed for a while I was losing power and the motor would only go so fast. Then one day when I was in the cove trying to tune my way out of it, it would go into gear but not move. For a brief minute it would only move in reverse but then that went away as well.

Here is what I have done so far. I pulled the cover for the shifter rod connection and that seemed to be just fine. I took apart the bottom end and noticed their were 2 keys for the key way in the prop. I am not sure if this should be 1 solid key or if it should be 2. I don't think the prop was free spinning, I don't remember now that it is apart, but I don't remember that being the case. So I am not sure if this is a problem or not. I also haven't come across a broken piece either. However when I looked online at the exploded diagram it seemed to be a solid 1 piece. I just am not sure if there are any variations to how this may be set up. Like the use of a different prop etc.

As I was looking at the gears, everything seemed to be fine, no abnormal wear etc. I tried to turn the drive shaft (the one that runs from the motor to the gears) by hand but it wouldn't move. This was after the shaft was no longer connected to the bottom gears. So I pulled the water pump out to dig further and I noticed one of the fins on the water pump had torn off (or broke off) and it had jumped from the spot it should have been to an opening between 2 good fins. I assume that was why I couldn't turn the shaft by hand.

A couple of questions. With the water pump fin being broken would that be a possible culprit to the slowing of the motor? Also if it got to the point it jammed or was turning slowly (as I didn't notice any issue with over heating or no water coming out) would that make it so the motor wouldn't move when in gear? I don't remember for sure that there was water circulating, but I also don't remember that not happening which I think I would have noticed.

I pulled my plugs and did a compression test, the top cylinder got 101 and the bottom was 105. Top plug looked good and the bottom looked to be a little rich. Can anyone let me know which jetting that may be from? Also I figure since we are still above 100 (barely) the motor is still good for a little while longer.

Any help would be appreciated. If you need more info I also provide that!

Thanks
Dan

 

[racerone]

A broken shearpin and a motor that is running on one cylinder.---Nothing to do with the carburetor.--Check for STRONG spark on both leads.

 

[flyingscott]

The drive pin in the prop should be 1 piece. You could also have a spun hub but try the drive pin first and replace the waterpump impeller.

 

[kos]

Yes I didnt check the spark but I will do that. The shearpin you are referring to is the one I mentioned on the prop correct? Sorry just want to make I am using the right language on this.

Spun hub on the prop I assume? Is there a way to test that without putting it all back together?

 

[flyingscott]

Yes

 

[kos]

thank you I will replace that while it is apart. I do have the new impeller already so that will be replaced too.

 

[kos]

I do have an update. Replaced the impeller and got the pin for the key way on the prop. Got the bottom end all back together and that did fix the prop issue (at least by hand turning it, it all seemed to engage properly). I also replaced the fuel pump just to be safe as I broke the screw. And Raceone was correct, I wasnt getting spark on the top plug, well not a strong consistant spark anyways. Bottom was very strong. Ordered the new coil yesterday. Hope once that is replaced this thing should be running right again. I will do some test and tune in a bucket once i get the new coil on.

 

[hardwater fisherman]

How did you determine that it was the coil that was bad? If you switch them and the weak spark follows the coil then yes. But if it is a 1974 model then you have points and condensers under the flywheel. It could be as simple as a bad spark plug lead. But it is more likely the points are dirty and need to be cleaned and gaped.

 

[kos]

Correct, that is what I did. I had previously swapped out 1 coil but never did the other. Spark is now great. However the motor seems to be missing, it struggles when I open the choke and will die out. I figured I would redo the carb now as I really should have done that anyways. Hopefully that will be the last of it and this will be running fine.

is there a recommended rebuild kit for these carbs before I start my search?