Making my own shear pins

[andrewhopkins]

I know they're not expensive but for a bit of metal they are.

Any reason why i cant buy a metre of steel rod to the same thickness for £10 and make 30 or more shear pins for myself.

Or is there something special in the build to allow them to "shear" as the name suggests ?

 

[charles_reed]

Use stainless welding rod - you don't say what engine they're for.

Example the Tohatsu shear pin is bronze and much softer than the stainless one for the Mercury, which is exactly the same engine.
You will run the risk if damaging the prop, especially if it's made of plastic.

Perhaps prevention is the best course - avoid running into things.

 

[graham]

I made some bronze ones out of brazing rod for my 5 hp yamaha .Not a great success as they sheared too easily.Using genuine ones now but may make some stainless ones.

 

[seahorse]

Re: Don\'t make your own shear pins

Yes Andrew it sounds easy doesn't it?
Thing is shear pins are designed to SHEAR at a specific loading which is decided by a combination of pin material, cross sectional area, hardness/heat treatmant of the material.
If you can acurately duplicate all of these then fine. If not you could end up with a pin that is not strong enough to take the full torque of the engine, one that will not shear until after the prop has been damaged or something somewhere in between. Any guarrantee would be void of course!.
Do it the safe cheap way, buy them!

 

[Danny]

Re: Make you own

I was a regular user of outboards on canals and a competitor in canal marathons until they cleared them. Breaking shear pins was a very regular occassion in the canals. I used to buy brass rod of the correct diametre and cut to size. Never had a problem on my old air cooled Yamaha 5 which saw me through over 12 marathons. I broke no more sheer pins in these events than others and because I could have a large number for a small cost never had to resort to cutting nails etc. The brass appeared to give enough not to shear with smaller knocks but sheered with the larger possibly damaging knocks.

 

[oldharry]

Re: Don\'t make your own shear pins

Seahorses' answer is of course technically entirely correct. However, talking about the average low HP engine of up to around 15hp, rod of similar material and the correct diameter is very unlikely to be so different to the original that it would cause problems either by premature failure, or by being so much stronger that it would allow prop damage.

When making replacement pins, use the same material. Particularly don't replace brass with stainless, as the stronger material could result in prop damage. In the same way substituting a stainless pin with a brass one will result in early failure as it will bend under load and be difficult (more likely impossible) to remove even in the workshop. There is also the probability of electrolytic corrosion if the wrong material is used.

Its very important is to ensure the diameter is exactly the same as the original: oversize will obviously not fit, but an undersize pin slopping around (and it will, however tightly you secure the nut) may damage the drilling in the shaft, as well as the prop, and may fail very quickly. It will also be extremely difficult to remove it as the pin will have been severely distorted by the time it fails, and will almost certainly need to be drilled out - usually only possible with a bench mounted pillar drill. Which of course we all carry on our boats for this purpose.....

As engine size increases, the loadings on the prop increase rapidly, and correctly manufactured drive pins become essential for all the reasons Seahorse gives.

 

[ccscott49]

reading all the other answers, I think I will stick to buying mine, of the correct type, how many do you shear a year? two, three? I've sheared one in ten years!

 

[andrewhopkins]

The Itchen

Only 2-3 a year but it always happens going up/down the itchen in my dinghy in deep water.

Its all the flotsum and jetsum going up and down the river which does it.

Once i had to row back up against the river, not very nice, so I wanted to tape a couple of pins in the dinghy just in case.

 

[ccscott49]

Re: The Itchen

Now I understand. But would still go with manufactured ones! then you are sure you have the correct type!

 

[Danny]

Re: The Itchen

If you are only going through 1 or 2 a year then it is not worth seaking out a supplier of the correct rod. On the canal I would go through 40 to 50 a year and all it cost me at that time was £2 to £3 for the rod plus a few minutes cutting the rod. Others using the manufactures shear pins went through no less number. Most engines has a rubber mount underside for storing 2 shear pins.