plastic impeller key vs. metal pin

[rednight]

Hi:<br /><br />I'm replacing the impeller on my 79 115. The impeller was seated with a metal roller pin, instead of the newer plastic biscuit. <br /><br />I was just curious when OMC discontinued using the metal pin, so I could get an idea of when the impeller was last replaced. <br /><br />Thanks!

 

[rickdb1boat]

Re: plastic impeller key vs. metal pin

Couldn't have been too long ago, as I replaced the pump on my 28 Johnson last year and it had the metal key. I don't know what's up with that "plastic", but I don't think the force of turning the pump would strain the key, even if plastic. But I do prefer the metal one, as the plastic may be more prone to crack over time. Course, I guess it would be good for a couple of years. Anybody know why they went to plastic or nylon or whatever it is?

 

[R.Johnson]

Re: plastic impeller key vs. metal pin

I would guess this to be a cost measure, if you look at the surface for the wedge key, it appeares to be forged, It show's no grinding, or milling marks. This would mean no further step's for machining, such as a drilled hole, or a key seat. But this is just a guess!

 

[muskyone]

Re: plastic impeller key vs. metal pin

i,m going to take a shot at this and say that plastic if something happend to the impeller and it jamed the plastic would shear and not tear up the shaft but just a wild guess

 

[bidlimit]

Re: plastic impeller key vs. metal pin

I just did the same job on my '86 28hp SPL and the pump had a plastic key. I don't think the pump was ever changed because the engine only has about 5 hours on it. So it must have been before '86 anyway.