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76, 35 hp impeller key, how to install?

R

relicshunter

Member
I am trying to install a new water pump on a 1976 35 hp evinrude and can find no info on which way the key goes. Other years it is real simple, 76's have a weird shaped key and the book says nothing. It was in with the square part toward the impeller and was worn away by the metal base plate. It looked like this beat up, scored key may have been what chewed up the impeller. I pulled apart another 1976 parts motor and found the key in the same way. I tried and tried to put it in the same way to no avail. I could with slight resistance install the impeller with the square toward the drive shaft and the curved part in the slot of the impeller. It makes sense that the impeller slides onto the curved edge and into place. So do both motors have it installed wrong?
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0317078
Please help. The water pump catastrophically failed while out scalloping and blew the head gasket with it. I don't need a repeat of that.
 
I assume that you're speaking of the weird looking curved nylon impeller key. If so, the flat portion obviously goes against the driveshaft... and as you're holding the key in front of you, the curved pointed portion of it faces left.

Apply a little sticky sealer of some kind on the key to hold it on the driveshaft.

Hold the impeller housing in your left hand (slight bit of grease on the impeller cup).

Spin the impeller into the housing cup in a counter clockwise motion with your right hand. Align the impeller so that the key groove will be in a proper position.

Slide the water pump housing and impeller assembly down the driveshaft and onto the key. Use a thin screwdriver (or something) to help hold the key in place as you lower the housing onto it.

Yes, those new nylon keys have always been a PITA!
 
Much easier to put key on the shaft with some grease to hold it.-------Then install the impeller on the shaft.-----Make sure shaft is driving the impeller.-----Now lower housing onto the impeller while turning the shaft.
 
It is this shape. 0317078.jpgIt goes in fairly easy with the curve towards the impeller and that makes sense, But two motors I pulled apart had it in with the square toward the impeller. On one it ground into the metal plate below the pump and probably caused the pump to disintegrate. The plastic key is such a better idea, and I've done a few with that. I just what to have it right since I already had to be towed back once with this motor.
 
Curve would go into the keyway of the driveshaft.--Post picture of that area on the driveshaft Post picture of the keyway or bore of the impeller.----Seems there may be a mix-up of parts.
 
As "racerone" states, a key of the type you have pictured would have the curved portion tapped into a machined curved slot on the driveshaft so that the squared off portion drives the impeller.

There are three types of driveshafts pertaining to the key that drives the impeller... (1) A slot for the wooddruff key, (2) A drilled hole for a short metal dowel like pin, (3) A flat spot for the nylon key that I assumed you were talking about. Which do you have?
 
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