Shear pin - replacement material

[pro-crastinator]

1956 Big twin.
Pulled the prop and saw that the shear pin was not looking well.
bent, nasty etc...
looks to be 1/4 inch brass - just like the brass rod I have in my toolbox that fits like a glove.
Am ready to cut off a piece and use it but something in the back of my memory banks thought it wise to ask.

Is the "pin" some wierd alloy - or will my quarter inch brass replacement be ok?
Not too soft? (can a shear pin BE too soft?)

 

[robert graham]

I've used brass rod for years without problems....the brass is fairly soft and likely to shear upon impact....to protect your motor's drivetrain....

 

[gm280]

I have a '76 40HP Johnson that had a shear pin that was bent from hitting something (previous owner as I got it). So I looked at it and thought that it was some type stainless steel and so I bought a new OMC/Johnson replacement for it. Seems the replacement is also either stainless steel or some type steel and not just copper or brass. But different type motors can and do take different type pins. So buy a factory type and see what you get. Then if copper or brass or even steel comes in, you can make another spare yourself... JMHO!

Let me edit this to state that the pin I was referring to was actually the prop pin on my OB engine and although it is a type of shear pin as well, it probably was not the same shear pin you are talking about. But the same suggestion still applies. That is purchase a factory original and go from there...

 

[racerone]

It was found that on bigger motors the brass shear pins would break.---Caused simply by shifting at too much RPM.---So they went to steel drive pins and shock absorbing rubber hubs.---This means that it most cases you will do $$$ damage to the prop.----Very difficult to change shearpins on a 100 hp motor hanging on the back of a boat too.--So they went to splined drives.----This means $$$ repairs if you hit something.----On that 30 hp motor you can use a brass shear pin if you are prepared to change the pin out on the water.--Have several spares and a steel one as the last one to put in.

 

[F_R]

OK, here are the facts: The pin was changed in mid-year 1956. Early models used part number 302566 SHEAR pin, made of Naval Bronze, 1-1/8" long. Late models used part number 304575 DRIVE pin, made of stainless steel, 1-15/32" long. They take different prop nuts, because of the different lengths. They also changed the propeller hub slip torque specs. Hard to tell what prop you have at this date. Probably the best guide is measure inside the prop nut to see which one fits.

 

[Crosbyman]

why not just buy one from your dealer...

 

[boobie]

On a motor that old, I'd still use the brass ones. Easier to change a shear pin than find lower unit parts. JMO.

 

[F_R]

On a motor that old, I'd still use the brass ones. Easier to change a shear pin than find lower unit parts. JMO.

Perhaps. And I'll bet that boobie has had to do that too. But I have to say that changing a shear pin in deep water is dang near impossible without going for a swim. Lessee, now what is that water temp up north at this time of year? In the first place, you have to hang your body out two feet beyond the transom to reach it. And you can't steady yourself by putting weight on the tilted motor because it will un-tilt and dump you in the lake. And even if you do take care of that problem, you still have to deal with the cotter pin, prop nut, broken pin, etc. Very likely you will have to drive the broken pin out with a hammer and some sort of a punch. If you don't drop a tool or part overboard, you are extremely lucky. Been there, done that.

If you want to do the job right, make sure you have the newer prop hub version, or just replace the prop. Then use the stainless drive pin and larger nut and a stainless steel cotter pin. And stay in the boat.

 

[pro-crastinator]

Great information.
When I get back to town, I will post pics of one beat up, craggy, nasty looking piece of marine grade bronze.
I really like the idea of a softer pin.
Heck, this one was last offered in early 56! And it did just fine.
Gimme a couple days for the pic.
Thanks

 

[gm280]

Just remember, the softer you make the shear pin, then more often you will be replacing them. IF the prop hits anything (like that will never happen :facepalm: ), it will shear the easiest material first. And while that sounds like a great idea, it also means you will be bent over the transom area fiddling with tools and replacement shear pins and such to get moving again... And after doing that a number of times, you will probably want something a little more substantial.... JMHO!

 

[Crosbyman]

with props not always available better to swap shear pins and if that engine is not to big just take it off the tansom and change the pin Inside the boat instead of loosing your tools or your last shear pin !

temperature of the water up north... currently below 32F pretty hard on shear pins !

 

[Chris1956]

On my Fat-Fifty, the drive pin was 5/16" Stainless, That pin would never shear.

I would think the brass is a god option as long as it holds full throttle. Better for the pin to be a bit weaker.

 

[pro-crastinator]

No Title

Looks like I have an original bronze shear pin from 1956. Replaced with stainless mid year. Also that the prop is in need of replacement with new "cap" and new stainless steel (longer) "drive pin" . OR, I could put in a new brass pin, pack toolbox well and continue to carry on.
I gotta say guys, option 2 is where I'm goin. It may bite me in the keester but time will tell.
Water temp today is 58ish. Crappie fishermen thick on the water. Too cold for a dip.

On a related note, pic 4 is of my newly aquired AD-12. Took Franks advice and went with a stainless bolt that fit nicely after grinding one edge of the locknut.
Note that the "nail" impersonating a cotter pin will be replaced after I replenish my cotter pin supply.

 

[F_R]

No Title

I'm confident that PJ35 prop is newer than 1956 and has the new style rubber hub, and a stainless steel drive pin would be proper. But it's your choice. BTW, here is what we are talking about when we mention the rubber hub