shear pin issues

[shootindave]

I have an early 70's Evinrude 25hp tiller. (title at the bank will get exact year)

I have two questions......

1) The motor seems to break shear pins for no reason. It has broke twice now without hitting anything. The motor does not slip gears or anything like that.

2) What shear pins should I buy.

** Motor history. I bought the motor from a friend who is knows a fair amount about boats 1 year ago, so Im guessing it had the correct shear pin / spare pin (the two that have broke).

P.S. i hope everyone carries extra shear pins with them...... mine broke after a duck hunt, below freezing, in the dark, 3 miles from the boat ramp. I wont go into the disturbing details, but I used a scew out off a shotgun sling as a shear pin and it got me home.

- Dave

 

[kenmyfam]

Re: shear pin issues

You need to make sure you have the correct shear pin. Wrong material will shear easier.
Welcome to iboats

 

[R.Johnson]

Re: shear pin issues

What size pin, and what is it made of?

 

[ezeke]

Re: shear pin issues

SB 1290 May help: please click the thumbnail.

Note that the stainless steel drive pin will break from repeated strikes if the propeller is not firmly seated.

 

[shootindave]

Re: shear pin issues

Unknown on size, but it seemed to fit well. Im 90% sure it was brass.

After doing more google searching I am wondering if my prop is to blame. It has a few battle scars from hitting stumps..... i read that this can cause over reving, which i think might cause a shear pin break.

I havent been able to find any other people with breaks when the motor is running great and you dont hit anything.

- Dave

 

[shootindave]

Re: shear pin issues

Ok.... the above instructions make me wonder. When the prop is in place and I screw on the end nut it doesnt fit snugly on the prop and still line up with the holes to put the pin to hold it in back in. I have to stop screwing it in to line up the holes.

 

[ezeke]

Re: shear pin issues

The correct stainless steel drive pins are readily available through authorized BRP dealers.

Use spacers -large nylon washers from hardware stores will work. The aftermarket props often will not seat tightly.

 

[kenmyfam]

Re: shear pin issues

Ok.... the above instructions make me wonder. When the prop is in place and I screw on the end nut it doesnt fit snugly on the prop and still line up with the holes to put the pin to hold it in back in. I have to stop screwing it in to line up the holes.

May need a small spacer to get the correct tension.

 

[ezeke]

Re: shear pin issues

If you get the model number off the transom bracket you can get the correct drive pin. There are two different ones for early and late years; early models used 314364, late used 307949.

 

[kenmyfam]

Re: shear pin issues

May need a small spacer to get the correct tension.

Stainless or brass shim stock will work if needed.

 

[ezeke]

Re: shear pin issues

Stainless or brass shim stock will work if needed.

You can run run your gearcase on ATF too, but I would not recommend that either.

Stailess steel comes in at least 100 different grades; you need the one that will do the job and still protect your gearcase.

 

[kenmyfam]

Re: shear pin issues

You can run run your gearcase on ATF too, but I would not recommend that either.

Stailess steel comes in at least 100 different grades; you need the one that will do the job and still protect your gearcase.

Do you mean for a shear pin ??? I was relating it to a spacer to align for the shear pin. (skinny take up washer)

 

[ezeke]

Re: shear pin issues

25HP OMC motors had drive pins.

 

[kenmyfam]

Re: shear pin issues

Shim suggestion was if wrenching it that far was a little much. Nothing else. Who knows what prop nut is on an older motor. Made one this summer for my buddies old Ted Williams. Works like a charm.
Thanks for the info though.

 

[shootindave]

Re: shear pin issues

what is the diffrence between a drive pin and shear pin? Mine is like the one pictured.

 

[ezeke]

Re: shear pin issues

Some propellers have only a shear pin to protect the motor when the propeller strikes an underwater object. OMC propellers had the rubber grommet between the inner and outer section of the propeller hub which would normally go first.

The drive pin will shear on impact but is usually not the first to go. If the propeller is loose the continuous strikes while running will eventually break the drive pin.

 

[soundchaser]

Re: shear pin issues

Sounds like the drive pin is possibly jumping out of the slot? Maybe it's jumping so much that it's taking out the drive pin. I agree with the shim idea.

 

[F_R]

Re: shear pin issues

Unknown on size, but it seemed to fit well. Im 90% sure it was brass.

After doing more google searching I am wondering if my prop is to blame. It has a few battle scars from hitting stumps..... i read that this can cause over reving, which i think might cause a shear pin break.

I havent been able to find any other people with breaks when the motor is running great and you dont hit anything.

- Dave

You say it was brass. That should be the end of the discussion. It is supposed to be stainless steel. Brass WILL shear.

 

[shootindave]

Re: shear pin issues

BTW its a 1970 Evinrude 25hp tiller. Anyone have the PDF service/owners manual?

So I need to buy a new drive pin and a rubber spacer to go in between the prop and the end cone thing to make the fit between them tight when the holes line up to put the pin in??

 

[ezeke]

Re: shear pin issues

A nylon spacer/washer would be preferable. The correct drive pin is #0314364.