1963 Big Twin... Do they have shear pins in the Lower Unit?

rennen · Jul 16, 2006

I looked through the manual, and to tell you the truth I am more confused now than before.

I ran aground yesterday, my prop is surprisingly in good shape, but the prop shaft turns easily by hand when the unit is in gear. It is a selectric shift model, and used to lock up if it was in gear.

Some guy at the dock told me to check if I had a shear pin and I hope that I do..

Any feedback?

rennen · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

Oh yeah 40hp evinrude

ezeke · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

The 65 model did and I think they are same. It is under the nose-cone. Take the cotter pin out.

Old part # was 304575.

Evinrude Boater · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

rennen,
I believe the shear pin is the cotter pin you have holding the prop on. I don't know of any internal shear pin. It would be problematic to replace an internal pin should you break it while at sea.
How is the thrust in the water? Have you noticed a difference lately while under heavy load?

Pony · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

I think some of the 40's in 63' had a cushioned hub, so its possible you just need a new hub.

Should be easy to tell. As ezeke says, remove the cone by removing the cotter pin. If there is a shear pin it will be hidden by the cone.

jimmbo · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

The cotter pin only holds the prop nut on. The so called Shear pin is really called the Drive Pin and made of a Stainless steel, very hard to shear. Drive line is supposed to be protected by a rubber hub in the prop. Take the prop off and check. If it has sheared you might have to use a punch to remove the remaims from the propshaft. When checking the electric shift the power has to be on and supplied to the shift electromagnet. If it is and it is not working, a broken clutch spring is most likely $$$.$

ezeke · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

The drive (shear) pin was used through 1986 on the pin drive 40HP gearcase. You will have no problem getting the proper pin from any dealer.

The pins were always designed to break to protect the gears, so don't use a substitute.

If the drive pin is intact, you may have spun the hub. A spun hub is not too big a deal either - just get a new Michigan prop here at iboats.;

tashasdaddy · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

pull cotter pin on cone, remove cone, remove prop. pin goes thru prop shaft.

rennen · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

OK Thanks for all of your responses.

I didnt realize that the shear pin was on the outside of the gearcase. I am familiar with the pin that you all are talking about, since I just changed my prop the morning before I ran aground.

The difference in thrust is basically that the prop is not spinning. Nothing whatsoever. It doesnt make any wierd noises like the gears are screwed up.. But the Prop stays motionless. I wlll check out that pin today...

I am a little confused though since one says that pin is stainless steel (which i know is very strong) and one says that it was designed to break... It seems that they would make it of a softer metal in order to promote the break in the event of an accident.. Any clairification?

Thanks guys

ezeke · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

See if it is broken or not. A little feedback never hurts.

tashasdaddy · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

some time the pieces get wedged, or the part left in the shaft shifts.

ezeke · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

Yeah, TD,

And sometimes the kind of help that people need cannot be provided in a a forum such as this.

OBJ · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

The shear pins are designed to break to prevent damage to the gears and prop shaft. All due respect to jimmbo, they are not stainless steel.

Paul Moir · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

The drive pin on a '63 Big twin is 1/4" stainless steel rod 1-15/32 long. It shears at about 200ft/lbs which is a bit above where the rubber hub is supposed to slip.

ezeke · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

To Paul Moir:

Is part #304575 the right one (drive pin)? I have the 65 parts manual but not the 63. I would like to mark it for future reference.

I know they used it in the 40HP Lark and 33HP Ski Twin as well.

Thanks

OBJ · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

Paul....have I been looking at this all wrong? Most shear pins I carry don't look stainless. Maybe a stainless alloy?

Paul Moir · Jul 16, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

Well, there's lots of types of stainless. I don't know for sure what type of alloy they were using but all the common ones have close to the same shear strenght so it shouldn't matter much. OMC just said stainless, which is a little like saying "steak" I suppose. Big differences between tenderloin and flank eh?

Ezeke, my numbers jive with yours. 304575 for the 40, 33 and 28hp as per OMC, and 35hp ('57-59) as inferred from my other charts.

OBJ · Jul 17, 2006

Re: 1963 Big Twin... Do they have shear pins in the Lower Unit?

Thanks very much for the information Paul. Guess I'd better take a little closer look at what my "steaks" are made of.

To Jimmbo....my bad....your right. My apology sir.

1963 Big Twin... Do they have shear pins in the Lower Unit?

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