Shear pins

[DavidSelf]

I am a new boater. I have been in lots of boats but I have never owned one until now. I have an old 57 Evinrude Fastwin 18 HP that I just had tuned and is in good running condition. the repairman was kind enough to show me how to start the motor and gave me the specs for the mix. My trouble is that I have never seen anyone change a broken shear pin. I am not even sure where the pin is. I do have two spairs but I see nothing that looks like them anywhere on the lower part. Can anyone take a few minutes to school me in this matter so I don't end up rowing several miles when I hit the lake.

 

[Esox]

Re: Shear pins

The shear pin goes through the prop shaft behind the prop. You will need to remove the prop to see the shear pin

 

[rickdb1boat]

Re: Shear pins

This should help:

OMC used several different methods of attaching the prop to the propeller shaft. The little 3 hp models had a threaded prop nut covered with a ?snap-on? rubber nose cone, although often the nose cone is missing. The 5 1/2's and 7 1/2"s had the snap-on rubber nose cone but no threaded prop nut; the prop was held on by the shear pin while the nose cone kept the shear pin in place. The 10's through 20's had threaded nose cones secured with a cotter pin, as did the 25's and 30's from the early and mid 1950's. The 35 hp model introduced in 1957 featured a plastic ?slip-on? nose cone secured with a cotter pin. Many of these plastic nose cones have been broken by people who put a wrench on them thinking that they were threaded.
The shear pin is located at the aft (prop nut) end of the propeller on some motors and at the forward (lower unit) end of other models. So just what is a ?shear pin?? It is a metal pin that locks the prop to the spinning propeller shaft and which is intended to ?shear? or break should the prop come into contact with a hard object such as a log or rock, hopefully sparing the prop or other engine components from damage. The shear pin is intended to be a sacrificial ?weak link.?

 

[F_R]

Re: Shear pins

You need, at a minimum, a pair of pliers to change the pin. In addition to a spare pin, you should carry an extra cotter pin.

Not meaning to start the usual long thread of arguments, but it is a drive pin, not a shear pin. It can be broken by really clobbering something hard, but that is not it's purpose. It's purpose is to connect the propeller to the shaft. The shock of impact with submerged objects is absorbed by a rubber hub in the propeller. The drive pin is part number 307949 and is made of stainless steel. The cotter pin is part number 306394 and is also made of stainless steel.

 

[BoatBuoy]

Re: Shear pins

David, for a visual, here is probably how yours is assembled. Item 51 is the drive pin (shear pin), item 52 is a cotter key.

 

[hammerhandle]

Re: Shear pins

Just an added tip, you might want to carry a small punch and hammer to remove a sheard pin, i have replaced my share of them by hitting rocks and stumps and it makes it easier to remove the broken part of the pin if it is bent.Its a good idea your looking at this before hand instead of trying to figure it out on the water. A spare set of plugs and a wrench to remove them would be a good addition as well.

 

[DavidSelf]

Re: Shear pins

Thank you all for your help. I really thank the one that had the pic of the parts. I now understand a little better. You all explained it so easy I now know how to change the broken pin. By the way, I took the 30 year old Duracraft out today and the 50 year old Evinrude ran like a champ. I did not catch one fish but I had the time of my life boating all over lake Texoma today. My Grandfather owned it, then my Father and Uncle and now I am enjoying it.

 

[samo_ott]

Re: Shear pins

That's great that your engine has been passed through your family to you. Hopefully you'll keep it in tip top shape to pass on also The 18's are great engines. I have several of them. Great power/weight ratio and easy to work on and get parts.