Shear pin problem?

[OldJohnson6hp]

1956 Johnson 15hp:

At low throttle the boat moves along just fine..mid throttle no problems..slowly accelerate and once at top end the engine revs up maybe a tad bit higher then normal except the boat starts slowing down <no propulsion> If I back off the throttle it will "catch" again and start moving..power it up and it loses it.

No clunks, clanks, or anything else odd.. Engine engages solidly in forward/reverse. Prop seems to be "biting" enough of the water..Thoughts?

 

[snake eater]

Re: Shear pin problem?

I would say its possibly the high speed needle/jet out of tune. I dont know if your motor has a high speed needle. If it does it may be too rich or lean, and usually the shear pin just breaks but if it caught in the housing then it may only catch at low speed and not in high, that's grasping at straws though.

 

[OldJohnson6hp]

Re: Shear pin problem?

Carb is fine..no engine issues. Seems to be in the drivetrain

 

[Bifflefan]

Re: Shear pin problem?

Sounds like a prop hub starting to go to me, It will get worse the more you use it like that.
Try a different prop and see if the problem goes away.

 

[OldJohnson6hp]

Re: Shear pin problem?

"usually the shear pin just breaks but if it caught in the housing then it may only catch at low speed and not in high,"


I though it was all or nothing either..but it seems to "slip". Like a car with a tranny thats going out.

 

[snake eater]

Re: Shear pin problem?

I would go with what bifflefan said, The hub is starting to go. I dont know if they are all made out of rubber but in any case if its old and worn it wont engage the propeller properly. Take it apart and check it out.

 

[lindy46]

Re: Shear pin problem?

Draw a line across hub and prop with a waterproof magic marker. Take it for a spin until you get the slippage, then check the marks. If they have moved, you have a spun hub. About a $30-40 fix at a Johnnyrude dealer.

 

[kbait]

Re: Shear pin problem?

Exact description of a spun prop hub. You may want to get a used one from tim's outboard 218-682-2331, and save your current one for a spare. Probably be less costly than re-hubbing the one you've got.