9.5 Evinrude shear pin mystery

Hello to all,

This is my first time here, awesome site.
I bought a 1968 Evinrude 9.5 hp recently and took her out 2 weeks ago for the first time . The motor runs good but I thought it would have a little more power than it did (jon boat 12' x 36" -2 guys and gear) Anyhow, I was tinkering with it and removed the prop just for giggles. The shear pin was broken in three pieces and was wondering how it ran seemingly ok and brought us back to the dock. I did notice that it pulled a little to the left (away from me). Is this normal for it to pull to one side?? Could the broken pin still been biting in somehow or should I notice increase power with the new pin?
Thanks guys

Re: 9.5 Evinrude shear pin mystery

welcome to iboats!

here's the thing - 12 ft jonboat is harder to run on plane than a 14, not sure why exactly, but it is. with a 14, she'd plane out & move on down the lake. try redistributing the weight forward a bit, maybe move the fuel tank up to the middle.

Also, since it's new to you, it's hard to judge just how much power to expect. couple things to try that might improve performance:

make sure you got fresh fuel (87 octane), the right spark plugs (champions) gapped properly, prop in good shape no dings or rough edges, the anti-ventilation plate even with the keel, maybe move the trim rod out a hole or two, rebuild the carburetor and water pump. Lighten the load as much as possible. 50 lbs makes a noticeable difference in that rig.

And a compression test and spark test.

I believe that when the pin breaks, the prop freewheels, so you must've had a piece or two in just the right place to make it spin.

Re: 9.5 Evinrude shear pin mystery

An old emergency cure for a broken shear pin is to reinstall the pieces in a different order. That will sometimes get you home. Anyhow, you obviously need a new shear pin. The correct pin is made of stainless steel and they call it a "drive pin" because it is not supposed to shear unless you whack something really hard.

The shear pin has nothing to do with torque steer. And I doubt you are going to get it to plane that little boat with that load. There just isn't enough bottom area to give you the lift. Sort of like trying to fly an airplane with half the wings cut off.

Re: 9.5 Evinrude shear pin mystery

thanks guys
you are right, it doesnt plane. I had a good running 6hp before and got this one hoping it would plane out. The motor itself is in good running shape,I can feel the difference in power but it just doesnt plane. i would of been tempted to get a bigger motor if you hadnt told me that a 12' is difficult to plane out.
One more question......how do I convince the little woman that I really "NEED" a bigger boat? :redface:

Re: 9.5 Evinrude shear pin mystery

accicentally fall in, on a warm day, at the ramp. say it is too narrow, to be safe.

Re: 9.5 Evinrude shear pin mystery

Or if your desperate .Get on the same side with HER and the rest is self explanitory.Its not hard to get a 9.5 running after it sinks.Hell theres a reason for a whole new rig.I bet you can get to fish more with your BUDDIES too,

Re: 9.5 Evinrude shear pin mystery

Back when those 9.5 motors were more prevalent, there was a lot written about the drive pins, including some Service Bulletins like SB-#1290. The problem was that if the propeller was loose on the shaft, the stainless drive pin would strike with each gear shift, and enventually break, or worse, damage the hub to the point of failure. The Bulletin also referred to the 20HP andd 25HP as having the same problem.

I have found some propellers fit fine and will hold tightly, while others will not. I now use nylon flat washers as spacers to make sure that the propellers are tight.

Another way that those pins get broken is by having your brother-in-law shift from reverse to forward with no hesitation with the throttle in the start position.

BTW, I have not found that my 9.5 motors will pull to one side or the other - unless they are not centered on the transom.

You might find that raising the motor higher and using a lower pitch prop will get you on plane. You won't have a great top end, but you will be able to plane. I've used the Michigan Wheel 6.5 pitch prop to push my 22 footer in calm weather while fishing and also to plane my 12' semi V. http://boatpropellers.iboats.com/Jo...rs/19/?**********=270439411&*******=821830379

Re: 9.5 Evinrude shear pin mystery

I also have the same motor and messing with the pitch cuold help. I also have a Johnson 10 hp that I have used on the same 12 ft aluminum boat with the same prop, and that 1/2 hp made an incredible difference. The only thing thats not the same in the 10 hp is a long shaft and 9.5 hp is a short. cant believe the shaft length can make that boat feel like its going at least 50% faster. Good luck

Re: 9.5 Evinrude shear pin mystery

I was out messing/cleaning/fiddling with this motor and decided to take the prop off and see what its #'s were. It's a 8 1/8 x 8. Seems like an odd size but thats what it is. Also is plastic, go figure.

Re: 9.5 Evinrude shear pin mystery

I think the prop is supposed to be 8 1/4 x 8 1/2, at least the '67 9.5 was. You sure you got the numbers right?

Re: 9.5 Evinrude shear pin mystery

The 8-1/8 x 8 plastic was one of the props listed in the OMC prop chart for the motor. Don't knock it. The plastic ones actually survived dredging the oyster bars as well if not better than the aluminum ones.

Re: 9.5 Evinrude shear pin mystery

The propeller that came with the 1973 9.5 was 8-1/8 X 8, PN 385940. The 1971 and 1972 had the same 8-1/8 X 8 but was numbered PN 383315.

Re: 9.5 Evinrude shear pin mystery

I remembered that the plastic prop on my 9.5 actualy came off of what I think is a '58 10hp Johnson. The one that came with the 9.5 spun so I replaced it with the one off the 10 which of course was plastic, I went to check the #'s on the aluminum one that came with the 9.5 and there are none. Sooo?