For duck hunting I often use my passed down Alumacraft 14 foot jon boat. A few years I purchased a small 4 HP Johnson for pushing my NuCanoe around in the swamp and eventually I started using it on the jon boat.
This particular motor has the weedless drive, and is a great little runner. Often it starts on the first pull. Alas, the last time I had it out I hit a stump and sheared off the propeller pin. The pin a designed weak point in the drive to prevent damage to the motor itself. No big deal, that’s what spares are for. I have even changed it out on the water before.
But, I was out of replacement pins (well I miss placed the three I thought I had) and after some online reading I decided to fashion my own out of stock brass rod. The correct diameter of the pin is 1/8″. I was not sure what the length was supposed to be so I waited till i got the old pin out before cutting the new one to length.
The first step is to remove the kotter pin locking the propeller nut to the drive shaft, once that is removed the nut will loosen and the metal washer and rubber seal will come off.
Once they are off, the propeller will be free to slide off of the shaft.
This then exposes the propeller bushing. This is what the shear pin locks the drive shaft to. It will pull off just like the items before.
Examining the inside of the bushing, I noted that one side of pin was still in it. I removed this and made sure all free pieces of the pin were accounted for.
As you can see in the picture, part of the pin was still lodged in the shaft. I had to use a punch to loosen it from its position in the shaft.
I measured using a caliper the inside diameter of the bushing. I then marked the stock brass and carefully cut it with a hack saw. After the cut was complete I used a file to remove any burrs from the rod.
I put the new pin into the bushing to check that it correctly fit. Once that was verified I then placed the pin the drive shaft and turned the bushing on the shaft till it lined up into the slot and locked in place.
I then reversed the process and re assembled the drive. After that was complete, I cut two extra shear pins and placed them in the motor housing. The previous owner had attached them in the same spot, following their lead I used electrical tape to attach them at different angles. That way when the spare is needed “in the field” it is easy to cut just one out.
An important lesson learned from using this motor over the years is to always be prepared to change this pin. I always keep a small multi-tool in my duck hunting blind bag for this reason, you never know when you may need it. As side note, about two days after this I found the bag containing the shear pins. But, hopefully someone in need of a pin will stumble onto this post and be able to make a pin. Till next time.
This reminds me of a story one if my professors in college told the class. He bragged about having a spare shear pin for his fishing boat, he would keep it in his wallet and would proudly show it to you to demonstrate his preparedness.
One day while fishing with a friend of his, he sheared the pin. (I think he was eagerly awaiting this moment.) With certainty and confidence our hero sprang into action. He got the boat close to shore and pulled the prop off. He then dug the remnants of the old key out and promptly dropped it in the water. He then smugly got out his coin purse and retrieved the replacement key only to discover that it was the wrong size! They managed to somehow find the old key and managed to make it sort of fit so that they could get back to the boat landing.
Thank you for putting this write up together. I have a 1969 4 hp seahorse that I recently sheared the pin off. I was actually looking for a replacement pin when I came across your article. Well you saved me some significant coin considering the replacement pin is $45 and 6 rods of 1/8th brass is like $10. One rod will probably make like 5 shear pins. Thanks so much for this!!
Glad to hear it helped out!