You probably don't want to do this, but a buddy and I cut a nail of the approximate diameter (12d or 16d, I think) and used it. Needless to say, it won't do what is designed to do, but works!! LOL

It was supposed to be just a temporary fix until we could find one, but ended up being permanent. LOL

Later
R3F

 

Those pins are made to shear off to protect your prop. I went the route of placing a nail in to replace and it works well. I only have a 45 lb. I try not to hit anything and do not go FULL power right off the start.
Your more powerful motor can shear the pins from starting in full power to take off many times as well as striking objects below the surface. Since your motor is so powerful it will shear pins when it hits something unless it breaks your prop first.
Keep spares handy and try to avoid underwater objects and have a spare prop with you as well if you use the stronger steel for pins.

 

That's a very good observation, LJ - we are probably starting full throttle and putting too much strain on the pin. Will start more slowly and see if that makes a difference.

The other thing I thought of is the prop. The prop has some pretty good dings in it and the tips are worn, probably not evenly. Would the vibration from an out-of-balance prop cause shears?

LOL, we're getting pretty good at changing out pins on the fly. Not a skill we really want to have though - it's a pain in the butt out on the water...

 

Good point...the vibration could be a factor as well! Get the best prop out there for the fishing you do and start out slow. Good luck.

 

I pulled the prop off my Minn Kota 70 and found 1/2 the pin sheered. I bought replacements at a bolt supply place.

 

I've sheered a few on my 70lb riptide. All of mine have broken when I accidentally stepped on the bigfoot button when the TM was up on the deck. In a pinch, an 1/8" drill bit cut to length will work on mine, but is extremely delicate/brittle.

Never sheered a single one on my old 55lb TM's. More power brought new things to look out for.

 

Try raising the motor up off the bottom out of harms way.
Could also be 70 thrust maybe too small for your 21 footer. .......ICM

 

I've never broken a shear pin in 35 years of using trolling motors, both Motor Guide and Minolta 50 to 80 ft-lb. Anytime it hit something a fuse would blow or circuit breaker would trip. Do you have a circuit breaker or fuse in the power wire?

 

We do, in fact my buddy just upgraded the circuit breaker from a little cheapie that was tripping every time we did an extended troll to a more expensive one.

 

I had an Edge 70 and bent those things all the time, you can buy from MK for like 50cents each, always bought 10 or so at a time, but they are designed to keep the armature from breaking, which was another problem I had with that motor.