Broken shear pin extraction tips?

Jeff Reardon

Jeff Reardon

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Hi folks.

I've got a Tohatsu 3.5 horse 2 stroke that came with a sculling boat I bought. It has a broken shear pin, and the pin is stuck on both both ends so that it will barely move. It looks as though both ends broke off, and then the former owner tried to remove it with a punch or something similar, and both ends got "smushed" (that's a technical term) and rounded over so that they won't slide out.

I've tried everything short of pounding on it with a hammer. I'm afraid the amount of force necessary to push it out would be enough to bend the aluminum the pin is set in. I took it my local "mechanic", who hates anything that's not a Johnson, and he said he was afraid he'd damage it and didn't want to work on it. (He also recently gave me grief about my "Yamadog". I think he hates Asian motors.) He suggested I try to pound it out, but confirmed my own sense that I'd probably damage things while doing it.

It's a stainless pin. Any ideas for how to drill it out, or perhaps grind down one of the ends?

Just in case it's not clear, I'm pretty inept with tools, but I do have a Dremel tool. Is there a bit for the dremel that would help? Other suggestions?

The motor starts just fine, and I'd like to put it back in action.
 
Hard to say without seeing it, but maybe try to find a small abrasive cut off wheel for your dremel, lowes and Walmart both stock them. A picture of what you are dealing with might help a lot. I have sheared quite a few pins on mine but never had this problem.
 
Yeah, I'd have posted a picture, but the camera battery is dead. I'm looking through my disorganized pile of bits and wheels for the dremel and found a pretty fine tipped grinding attachment that I thinks is intended for sharpening a chain saw. I'll give that a try in the am, and take pictures if I can't make progress so folks can give more directed help.

Thanks.
 
I've broken shear pins twice. Both times the pins needed to be punched out.

Did you say the pin is aluminum? If so it ought to be easy to drill out.
 
Unfortunately, the pin is stainless, and its in a hole drilled through aluminum. I'll take a shot at it before the second cup of coffee gets my fingers twitching.
 
I have always used a sharp pointed finish nail and pounded the pin out. But the pins were always something soft. I've never heard of a stainless shear pin in an aluminum shaft. Sounds like a recipe for shearing the shaft.
 
According to the owner's manual, these pins come standard in brass, but there is a stainless replacement. My pin is definitely not brass.

Part of the issue is that the motor is so small that I'm afraid I'm going to bend things if I have to do any amount of banging on it.
 
Jeff can you take off the propeller ? Stainless is harder than the aluminum so you are right about not driving it out with a punch. The pin should have been brass, copper, or aluminum. You can drill it out. That is not as easy as it sounds. I have drilled a lots of stainless. The trick is... drill as slow as you can. One fast spin of the drill and your drill is dull. You should see little filings coming off the stainless then you are drilling at the right speed.

Start with a small bit as close to center as possible and the move to a larger bit. Take your time. More than likely the stainless bent rather than shearing straight off like brass or copper would have thats why it wouldn't drive out.
 
Jeff,
get a block of lead to work the part on. A bar works best. (Boat weight and keels)
The Dremel tool is your friend to get a good flat on the S.S., use the fine tip stone grinders.
You then want to get a very sharp pin point dead center if you are thinking about drilling at all. I would only drill just to the edge of the AL so as to relieve the peened edge. Stay a drill size just under hole dia. of the pin.
Then use the lead to support the AL shaft and drive the pin out into a hole drilled in the lead with a heavy hammer and a small punch. The hammer needs to be heavy so you can just tap and get the pin moving.
If you know someone with a C press that is very helpful, but you need a good size one. I dont like a hydraulic press as you don't get any feel and cant stop it once loaded up easily.
 
Jeff some prop shafts are chrome plated, try a file first. If the file skids on the shaft, its chrome plated & grinding will go thru the plating alowing rust to form (stuck/rusted prop or pin). If the file cuts into the shaft its stainless & not so much of a problem. Get rid of the burrs on the end of the pin & lay the motor on something solid, blocking the shaft solid on the bottom side for support, 2x4s will work fine, use enough blocks to keep the cavitation plate off the bench & drive the pin strait down into the supporting blocks & the pin should slide right out. Good luck!
Dennis
 
I'd soak it in breakfree & try to drive it out.

Has to be braced on something absolutely solid.

If you try to drill it out I wouldn't use anything except a drill press where you have slow speed.
 
Have the same motor,only a Nissan. It had brass shear pins, and I had the same trouble. Instead of shearing off cleanly it bends the pin over slightly then breaks. Mine has a composite prop and once the pin spun a groove in the inside of the hub of the prop. There was no way to get the prop off in the field, which made for an enjoyable paddle home. I supported the shaft on wood blocks and carefully drove the pin out with a small punch. Stainless, being harder, will no doubt be harder to do. It may help to file the end you drive. I always thought a metal prop would help reduce this problem, but I never have seen one listed, for a Nissan.
 
Thanks for all the advice. I ground off the burrs on one end of the pin and drove it out. It turned out it was a short length cut from a machine bolt or screw--so I guess the pin had broke before. LOL.

Any way, on the the next problem--see new post!
 
Thanks for all the advice. I ground off the burrs on one end of the pin and drove it out. It turned out it was a short length cut from a machine bolt or screw--so I guess the pin had broke before. LOL.

Any way, on the the next problem--see new post!
 
Jeff,
buy three from your dealer. Keep one zip tied up in the motor cover somewhere.

Good luck.
 
Jeff,
buy three from your dealer. Keep one zip tied up in the motor cover somewhere.

Good luck.
Click to expand...
That good advice,,,I use to do alot of commercial fishing and we always had one taped to the handle,,,I was out in Lake Ontario once with an old 18 Johnson and the pin sheared off and we didn't have one this may be hard to believe but I pulled a 2 1/2 inch nail out of the top of our 16 ft punt and made a get us home pin,,,,Chuck
 
I once made it home with fishhooks jammed into the shearpin hole on a 3 1/2 hp. Champion. Learned something valuable that day.
 
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