Gearcase or Spun Prop Issue?

[bryans1]

My 1971 Evinrude 18102 suddenly will not go above 1-2 mph. As soon as I give it throttle, the RPMs increase as expected but the boat speed does not increase. The shear pin in intact. Can go in reverse slow too. Any ideas as to the problem?

 

[Bifflefan]

Re: Gearcase or Spun Prop Issue?

Sound like it could be the prop. I'd try a different one and the proof will be in the pudding. If it goes then it was the prop. If not.........................

 

[wilde1j]

Re: Gearcase or Spun Prop Issue?

Sounds like a spun prop hub. Easy to confirm ... just put a mark on the central metal hub and one on the outer hub metal. Run the boat under load ... if the two marks move, relative to each other, spun hub. Take prop to a prop shop to be rehubbed.

 

[bryans1]

Re: Gearcase or Spun Prop Issue?

Can a prop with a intact shear pin spin? If so, perhaps you are right.

 

[wilde1j]

Re: Gearcase or Spun Prop Issue?

Is this a hydroelectric shift motor?

 

[bryans1]

Re: Gearcase or Spun Prop Issue?

I do not think it is an hydroelectric shift motor based on another thread I read from "Seahorse" that reads. "If you have a prop with a drive pin (shear pin) in it, you have the electric shift gearcase, with springs and electro-magnets." I have a shear pin. It shifts into gear fine but, seems to slip when I accerate the throttle. ***One operating difference over the span of two weekend is... on weekend one I had the motor running fine attached to the 12 volt battery, whereas weekend two I ran it without the battery as it was dead and the issue surfaced after a few minutes of planning near full speed. Does shifting require the battery?

 

[wilde1j]

Re: Gearcase or Spun Prop Issue?

Mechanical shift doesn't need a battery. Hydro-electric does.