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Thread: No shear pin surprise

  1. #1
    Getting the hang of it

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    Default No shear pin surprise

    I recently bought a new boat with 20 HP motor. To my surprise the motor has no shear pin. I previously only had experience with 2 HP and 5 HP motors and I realized that large motors should not have a shear pin, but I thought that 20 HP is small enough to be with it.
    In the past I got several occasions when I cut off the shear pin due to heating underwater objects. I usually was able to replace it even without getting out of the boat.
    My question now is what should I expect with the motor without shear pin if I hit a submersed object? Well, I realize that on the full throat it would be disaster for the motor and, probably, everybody in the boat, but generally speaking, is there any protecting mechanism/devise in the modern motors to substitute the function of shear pins?
    Thanks!

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  3. #2
    Has too much time on their hands

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    The prop has a rubber insert between the shaft and prop. If you hit hard enough, you may “spin” the prop. That is to say the rubber sheers away from the prop, rendering the prop useless.....
    Been there, done that on a 20h merc......they will take a pretty good whack though. Blade damage would show up before a spun prop though.

  4. #3
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    Thanks for the reply!
    What do you think, is it possible to replace this rubber insert in the field?
    I go fishing to Georgian bay sometimes quite far and I'm now thinking what should l do in case I damage the motor.

  5. #4
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    I know my merc had to get a new prop as opposed to replacing the hub. If you are concerned, carry an extra prop.

  6. #5
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    I have Tohatsu 20HP. As far I could learn it is the same motor as Merc 20 HP.
    Yeas, I consider to have a spare part on the board, but I want to make sure I can change it if it breaks. I have good mechanical skills, but never done it before on this motor.
    Is it correct that I just need to change the propeller? That's what are you saying?

  7. #6
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    Quote Originally Posted by MarkD View Post
    I have Tohatsu 20HP. As far I could learn it is the same motor as Merc 20 HP.
    Yeas, I consider to have a spare part on the board, but I want to make sure I can change it if it breaks. I have good mechanical skills, but never done it before on this motor.
    Is it correct that I just need to change the propeller? That's what are you saying?
    Yes.....it’s very easy to change a prop. Take yours off to see how it’s done. Keep in mind though, that a hit bad enough to spin your prop will no doubt cause other damage. The prop blades for sure, and quite possibly the shaft as well. That’s what happened to mine...

  8. #7
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    On a bigger motor I hit something once I think a piece of floating bog, it did no damage to anything other than spinning the prop, didn't have a spare. I was able to limp back, basically at a trolling speed. If I tried to go faster it would just spin again. Don't forget to have the proper wrench to take the nut off and a tool to flip the tabs up or the pin out of the nut. there will be something to hold the nut in place. I now carry an extra prop and equipment to change it.

  9. #8
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    Thanks! Very valuable info for me. Appreciate your replies!

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