Shear Pins for 1973 20 HP Johnson

[Murfreesboro1]

Hey gang,

I sheared a pin today and had to paddle about 3 miles. I was just trying the motor from the repair shop within the same area of the shop so if it did not run good I could take it back. My questions - is there another material that could be used that is a little stronger than shear pins??? Can a person use a little stronger material and get a propeller with a rubber bushing instead of shearing pins??? I am thinking about a prop guard, any recommendations???

The motor ran really good except at idle, it would spit and sputter and cough more than I think it should. Any suggestions on how to smooth this out???

Appreciate the inputs in advance!!!!!

 

[ezeke]

Re: Shear Pins for 1973 20 HP Johnson

You should be using the OEM drive pin - Part #307949. It is stainless steel. The OEM propellers do have rubber bushings between the inner hub and the outer. The Michigan Wheel aftermarket propellers have the bushing as well.

You don't want to go too far with hardness on the drive pin, it's a lot easier to replace that than the gears that will break instead.

Be sure that the propeller is tight on the propeller shaft when you finish installing it. If the propeller swings loose on the shaft it will bend the drive pin back and fourth until it breaks.

BTW, If you cannot adjust the propeller nut to hold the propeller firmly, you may find that nylon plumbing washers available at hardware stores will fill the gap between the propeller nut and the propeller.

The OEM propeller Guard was part number 172334. If you want to try to find one, you could keep a search running on Ebay or try sea-way.com in Seattle WA.

If you are sure that the high speed orifice in your carburetor is clean, you might find that Joe Reeve's instructions on setting the needle will help: http://forums.iboats.com/showthread.php?t=167352

 

[HybridMX6]

Re: Shear Pins for 1973 20 HP Johnson

I agree with that, don't use something stronger than the factory material. That shear pin is way cheaper to replace than a lower unit or a prop. Just buy some spares and keep them with you on the water. I know I've had to stop and change them on the water before. Good thing is a fish shallow waters in saltwater, so I just have to get out, but it's a lot easier than paddling a boat 3 miles.
I had a '71 20hp, it was a great motor except the water pickup, I prefer the newer styles with the thru-hub exhaust. I had problems with my boat causing cavitation with the old style.

 

[F_R]

Re: Shear Pins for 1973 20 HP Johnson

If you use the 307949 Stainless steel pin, it shouldn't be breaking on you. Is it possible to break it if you mortally clobber something? Yes. That's why they invented spares.

And yes, the prop has a rubber hub, you just can't see it. An exception again has to be made for something that wasn't made to be on there.

 

[Howard Sterndrive]

Re: Shear Pins for 1973 20 HP Johnson

The motor ran really good except at idle, it would spit and sputter and cough more than I think it should. Any suggestions on how to smooth this out???

running a couple tanks of fuel through it often gets them idling better. New spark plugs can make a big difference on these motors regardles of what the existing ones look like. If that stuff doesn't work, the link n' sync process of adjusting timing advance to throttle linkage might help. Beyond that, After verifying a bright blue spark jumping at each plug, a carb kit/cleaning would probably be in order.

 

[samo_ott]

Re: Shear Pins for 1973 20 HP Johnson

Something also to note for anyone reading this is you can usually jerry rig the busted pin and limp home.

After the pin breaks (shears) you usually have 3 pieces, 2 tiny pieces on the outside and 1 larger pieced through the prop shaft. If you carefully remove the 3 pieces and put the larger piece on one end and the the 2 tiny pieces together onthe other end, it usually holds enough to get home at low speed. I have not tried this though but I have heard it works and it makes sense that it would,

BTW, did you hit something to break it? It must have been quite hard?