57 johnson 18hp water pump impeller key

[riverbronzeback]

Water pump quit working so i pulled apart to replace impeller. Impeller looked new but i noticed the key on the driveshaft that spins the impeller was sheared off. I have parts motor so took it apart and replaced key. Put back together and worked fine and was pumping water great. After a couple of minutes i noticed it quit pumping. Pulled back apart and same thing. It appears the driveshaft is dropping down to far into lower unit and shearing it off. Why would this happen? It is only a matter of 1/4 inch but that is enough to slide it down through the thin plate under water pump housing. Would love to take pitures but camera is down at the moment. Sorry. This is the last thing i need to figure out to get this thing running. Changed plug wires, condensers, coils, cleaned and set points, converted to fuel pump, rebuilt carb, compression is 105 on both cylinders. Purrs like a kitten. Hopefully this is nothing major.Thanks

 

[crazymanme2]

Its been awhile since I had that old of a motor apart so is there a flat on the drive shaft or a key way cut in?

 

[riverbronzeback]

Doesnt look to be a keyway. Top of driveshaft is squared with an o-ring. Bottom which goes into lower unit is splined so it slides right in. I see nothing that looks like it would hold it in place. Have newer manual that cover later early 70s 18hp and looks their is part they call "retainer" , looks like it goes on bottom of driveshaft. Could i be missing this part? Thanks. Will work camera to post pics hopefully.

 

[crazymanme2]

The retainer they are talking about could be like a spacer but not quarter inch which you say it is too low?Pics would be nice.Is bottom of drive shaft have a place for a snap ring?

 

[riverbronzeback]

After doing a little more investigating it looks like drive shaft sits in the pinion gear in lower unit. My lower unit off parts motor the driveshaft sits the way it is supposed to. Will try to put that one together once i get another key for impeller.

 

[riverbronzeback]

Just so everybody knows i did piece together a lower from the two i had torn apart. I couldnt figure out why parts wouldnt work from one to the other. The lower units were dif. One had clockwise gears and the other had the opposite. Took a little while to figure out. Driveshaft from one, and gears from the other. Somehow it worked. Motor runs great. Just fineshed paint job. Will post pics when done. Thanks for suggestions.