Shear Pin Size 56 fleetwin

[Kelpy]

I have a 56 7.5hp fleetwin and a 53 15hp fastwin, what diameter is the shear pin? I know they are the same diameter I just don't know what it is. Trying to make some out of brass rod to have some extras and maybe protect the prop a little. I do a lot of duck hunting and motor in stump and long infested waterways so some extras would be nice. . .

Thanks, Kelpy

 

[Arctic 33]

Re: Shear Pin Size 56 fleetwin

I think they are steel drive pins. They are on my 10 hp 57 johnson.

 

[HighTrim]

Re: Shear Pin Size 56 fleetwin

You have two different systems there Kelpy.

On your Fastwin, you have a shear pin, part number 301923

On your Fleetwin, you have a SS drive pin, part number 302333

Never use a drive pin where there should be a shear pin or you are going to have a damaged lower unit/powerhead where you would normally only have to replace the shear pin.

 

[Kelpy]

Re: Shear Pin Size 56 fleetwin

SO, I don't understand what the difference is between the shear pin and drive pin

I know the shear pin is the only thing that keeps the prop going and when something hard is hit it breaks, saving the prop and lower unit. . . What is a drive pin and why doesn't things break when you hit something?

I have seen props with rubber bushings in the middle of them to allows slippage when something is struck, but this prop doesn't look like it works that way? To me it looks like it is simply a shear pin under the rubber cap. . .

Sorry for the noob question. . . Kelpy

 

[Cheetah 210es]

Re: Shear Pin Size 56 fleetwin

A shear pin is your weak link designed to break before anythings damaged. Think of drive pin as a 100 amp fuse and shear pin as a 10 amp.

 

[HighTrim]

Re: Shear Pin Size 56 fleetwin

It was in the mid 50s that cushioned hub props were introduced. These props hubs absorbed the impact of a hit, rather than the shear pin. The props were still locked to the shaft, buy but a DRIVE pin now. Some models used slip clutches to take the brunt of the blow.

With the drive pins, it is important to properly tighten the prop nut, too loose and the drive pin will wear on the inner hub of the prop. You tighten them as much as possible by hand, then with a wrench continue tightening until the cotter pin hole is aligned. Backing off instead of tightening will cause the wear I mentioned, resulting in prop failure.

 

[nwcove]

Re: Shear Pin Size 56 fleetwin

get your trusty drill bit set out, find the right size bit......use the end that goes into the drill tho, trim to lenght and you have it. and as mentioned, dont replace a shear pin with a drive pin.

 

[F_R]

Re: Shear Pin Size 56 fleetwin

Your Fleetwin uses a 3/16" stainless steel drive pin because it has a slip clutch built into the geacase. Your Fastwin uses a 3/16" drive pin because it has a rubber cushion in the propeller. You can't see it but it's in there.

 

[nwcove]

Re: Shear Pin Size 56 fleetwin

just curious, but would replacing a ss drive pin , with a brass shear pin cause any problems under normal operation?

 

[HighTrim]

Re: Shear Pin Size 56 fleetwin

just curious, but would replacing a ss drive pin , with a brass shear pin cause any problems under normal operation?

Depending on the motor, just might end up with alot of broken pins Although I use shear pins in my 1953 15hp Fastwin, which brings me to my next apology....

Sorry Kelpy, listen to Frank, I was sure my parts list had listed shear pins rather than drive pins for your(our) model.

 

[F_R]

Re: Shear Pin Size 56 fleetwin

Using a brass pin won't hurt anything, unless you fall overboard while changing it and die of hypothermia. Seriously, you will be changing it often because it will wear out just from the bang it gets just from shifting. I guess some people like to change them, just part of the experience.

 

[TN-25]

Re: Shear Pin Size 56 fleetwin

I thought the Fleetwin 7.5, plus the 5.5 & 1965 6-horse motors used a shock absorber on the drive shaft rather than a rubber splined prop hub. For 1966 the 6 lost the shock absorber & went with the rubber splined prop hub. It is for that reason that the 1966+ props were purposely made to not be interchangable with the older models, so that you could not put an older non-rubber-splined prop on the newer solid drive shaft 6s that didn't have the shock absorber on the drive shaft.

 

[F_R]

Re: Shear Pin Size 56 fleetwin

I thought the Fleetwin 7.5, plus the 5.5 & 1965 6-horse motors used a shock absorber on the drive shaft rather than a rubber splined prop hub. For 1966 the 6 lost the shock absorber & went with the rubber splined prop hub. It is for that reason that the 1966+ props were purposely made to not be interchangable with the older models, so that you could not put an older non-rubber-splined prop on the newer solid drive shaft 6s that didn't have the shock absorber on the drive shaft.

Agreed, that's what I just said up above. Fleetwin uses a shock absorber. Except I called it a slip clutch which is actually what it is. You tangle with a stump, the spring in the shock absorber winds up and releases (slips) until you are clear of the stump, then the spring unwinds and drive resumes. But a brass pin will shear before the spring releases.

It seems like an awful lot of those shock absorber springs are breaking lately, even without hitting anything. My unproven suspicion is that it is from nothing but metal fatigue resulting from old age. That is a very strong spring under constant stress whether running or not. I think it is just getting tired of the 60 year stress and snapping. Most of them did fine for the first 50 years.

 

[TN-25]

Re: Shear Pin Size 56 fleetwin

Your Fleetwin uses a 3/16" stainless steel drive pin because it has a slip clutch built into the geacase. Your Fastwin uses a 3/16" drive pin because it has a rubber cushion in the propeller. You can't see it but it's in there.

Ah yes Frank, you did already mention that.

Sorry, I'm a little slow on the uptake today. Happy New Year!

 

[F_R]

Re: Shear Pin Size 56 fleetwin

Just agreeing, not arguing. And clarifying for those who don't know how it works.

 

[Kelpy]

Re: Shear Pin Size 56 fleetwin

Thank you all for the clarity! I appreciate it, would be lost without this forum. I'm in my early 20's and these motors were way before my time and your knowledge has helped me with affordable power for my little duck boat! It is much appreciated!

On a side note, some times when I'm running with the 7.5 it just starts slipping and doesn't go anywhere, motor winds up but it doesn't spin the prop. But when I stop, put it in reverse, and then in forward again it goes fine. It only does this once in a while and mostly when it is under full throttle and a heavy load (2-3 people). I'm guessing this is a sign of a weak/broken spring. . . ?

 

[F_R]

Re: Shear Pin Size 56 fleetwin

I suppose that is possible, but they usually get very tight and/or stall when it breaks. But not always. It sounds more like cavitation. Are you running in weedy water? That will cause it. Putting it in reverse sheds the weeds. Too high on the transom will also cause it. As will ANYTHING that causes air bubbles in the water ahead of the prop.