71 Johnson 25 HP troubles

[flathead78]

I have owned a 71 25 HP johnson for 5 years. Ran great the first four. Last year I started shearing the shear pins. I can putt around at idle just fine but when I open up the throttle the motor bucks and then the pin goes. The lower unit oil was changed every year and there is no evidence of water in the lower unit. Does the whole lower unit need replacing or is there a simpler(cheaper) solution? Motor starts and runs great hate to scrap it out. Any input is appreciated.

 

[G DANE]

Re: 71 Johnson 25 HP troubles

I had the same problem, but it turned out I torqued the propnut too hard. The pins actually bent to the point of shearing already when I tightened the not. The nut is cutter pin locked and should only be next to finger tíght. This was on a 73 25 HP exactly same motor.

 

[Chinewalker]

Re: 71 Johnson 25 HP troubles

Hi Flathead,<br /> I am guessing your issue is less with the pins and more with the bucking. The bucking is indicative of a worn clutch-dog. It is the part that engages the forward and reverse gears to the propshaft. As it wears the working surfaces round over and they don't hold their bite on the engaged gear well enough to stay in gear under acceleration or heavy load - hence the bucking effect. Almost feels like you hit a log, does it not? <br /> Not a difficult or terribly expensive part to replace. A good manual is a must. Don't run it like it is, as it will eventually wear on the gears as well and THEN you'll have a much more expensive fix. <br />- Scott

 

[flathead78]

Re: 71 Johnson 25 HP troubles

Thanks Scott that makes sense. Just as you said it is like hitting a log (I have hit plenty).