BRP Water Pump Instructions Wrong?

[beerman57]

Says to measure D/S thickness at the key (biscuit) location and use the large/white biscuit for the small D/S and the small/black one for the large D/S – makes sense to me. So, I know getting the impeller down over the biscuit can be a little bit of a challenge, having done many. But after at least 10 minutes I gave up on the white biscuit and tried the small/black one and still took 5 minutes (normal to me). Halfway expecting a lot of play between the impeller and D/S, but no, just a little like normal. Now I know it’s very possible to measure a small D/S wrong and figure it’s the large, but I don’t see measuring a large D/S wrong and thinking it’s a small. I’m stumped as usual, but since there is very little impeller play on the D/S, it’s going on that way! Also the calipers I have seem to be OK, at least they read O when fully closed.

[fleetwin]

Which kit/hp is this for? It just seems like you are describing the same kit for two different diameter driveshafts….But, if this is the case, BRP would have had to supply two different impellers, one for each driveshaft diameter. So, I too, am confused.

[beerman57]

Nope, measuring from the flat where the biscuit goes to the other side of the D/S, there is only .049" difference. kit #439077. It’s not the shaft diameter, it’s the depth of the keyway cut.

[fleetwin]

OK, I think I understand now….So, your driveshaft flat/cutout measurement called for the larger key, but it wouldn’t fit, you had to use the smaller key. Do you still have the original key you removed from the old pump? I have never experienced this kit so am not much help.
Too bad the driveshaft on this engine doesn’t just pull out so you could have a better look at what is going on with the impeller/key fit.

[beerman57]

It’s a new D/S, converting the motor from LS to SS. Doesn’t matter much now, I’m FUBAR on this motor after today!

[Mumbles]

I’ve had new OMC/BRP water pump kits which contained BOTH keys. I just use the one which fits making sure it and the impeller are oriented in the correct way.

[dan-in-tn]

Mumbles is right. It’s the flat that is different. Just use the key/wedge that works.
The impeller is suppose to rock back & forth thus not wearing the shaft in the same place. If the impeller has an oring underneath it use the oring to hold the wedge up against the shaft. Notice where the opening is for the wedge in the impeller. Usually on a leg of the impeller. Slide the impeller down over the shaft and onto the wedge which pushed the oring down into place. If no oring under the impeller a small screwdriver & a dab of grease will keep the wedge in place. (I am assuming you are not putting the impeller in the housing?). Once the impeller is on the shaft sitting on the plate, I just put some dishwashing liquid on it and the housing cup. (I have glued the oring into the housing groove previously). Now put the housing down over the shaft and turning the driveshaft clockwise push down on the housing. The impeller will rotate into the housing. Mount the housing down, your done. Is that the way you are doing it? I do all of my OMC water pumps that way. The bigger the impeller the easier they are. Dishwashing soap works well and disappears on start up. Cheaper than grease!

Dan in TN

[Michael Anfossi]

I have slightly sanded the larger key or put a slight bevel on the top of it to aid the installation of the impeller. Works for me. I have tried the smaller key but always felt it was just a little too loose.

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