Broken drive/shear pin when shifting to forward/reverse, Sea Horse 20 (FD-20C)

[clicc916]

My dad gave me his 1966 Johnson Sea Horse 20 (FD-20C). He said that he'd have problems with the drive/shear pin breaking when he took the boat out. He would put in a drive pin, test it out at home, then take it out to the lake. As soon as he shifted into gear (whether forward or reverse), the drive pin would snap and there wouldn't be any propeller movement.

Last week, I replaced the drive pin (3/16" x 1 3/8" stainless steel pin, part number 0307949). I tested the motor out at home, started up (not running perfectly but working) and got the prop moving. Yesterday, I took the boat out to the lake, started her up in neutral, shifted to reverse and--nothing.

Another broken drive/shear pin and all that work for nothing. I've searched this forum but couldn't find anyone with a similar problem. It seems as though the drive pin snaps when I apply torque to the drive system but it shouldn't cause that much stress, should it?

I'm a total outboard newbie, and I don't have the manufacturer's manual. However, I do have a SELOC, Glenn's, and Chilton's manual of older Johnsons that I borrowed from the library. Thanks.

 

[Chris1956]

Re: Broken drive/shear pin when shifting to forward/reverse

Re: Broken drive/shear pin when shifting to forward/reverse

There should never be enough stress to break the pin, unless you hit something hard. Does the prop spin free on the prop shaft? Does it hit the gearcase or A-V plate? Can you push in on the propshaft? Does the prop catch on soemthing when you do so?

 

[tashasdaddy]

Re: Broken drive/shear pin when shifting to forward/reverse

Re: Broken drive/shear pin when shifting to forward/reverse

that is the part # for the newer motors, don't know if it is the one for your motor.

 

[clicc916]

Re: Broken drive/shear pin when shifting to forward/reverse

Re: Broken drive/shear pin when shifting to forward/reverse

Chris1956-Before I took the boat out on the water, I was able to spin the prop freely with my hand. It didn't it the plate, and there was nothing under the prop when I attempted to put it into gear. So by "pushing in on the prop shaft" do you mean pushing into the prop (force applied parallel to the ground)?

tashasdaddy-All my attempts to search for drive pins came back with that number.

 

[F_R]

Re: Broken drive/shear pin when shifting to forward/reverse

Re: Broken drive/shear pin when shifting to forward/reverse

Chris1956-Before I took the boat out on the water, I was able to spin the prop freely with my hand. It didn't it the plate, and there was nothing under the prop when I attempted to put it into gear. So by "pushing in on the prop shaft" do you mean pushing into the prop (force applied parallel to the ground)?

tashasdaddy-All my attempts to search for drive pins came back with that number.

That is the correct pin. There are few things that will break them.

1. Shifting at high rpm. You should only shift at idle.
2. A worn hole in the propeller shaft (wobbled out). Or a worn pin groove in the prop.
3. The hub frozen in the propeller. Normally the rubber shock hub takes the stress, but if it is all siezed together, it can't.
4. A brass prop. That's ok, but you must pay particular attention to #1