Found spare part on ground after pulling shaft for water pump

[Dwayn66]

Today, I pulled the bottom unit to replace water pump on my 75 hp force mercury (1996) motor. Lowered motor to vertical, went into shop to tear apart water pump, came back out and found a part laying on my tarp. This part does not match a single part from my diagrams. it is 1 in in dia. and 1/2 inch thick made from hard plastic, that has groves cut into it like it belongs on a shaft. After I finished repairing water pump, it would fit on top of shaft and slides down to end of keyways but it was not on there when I took it off. Any help would be great, don't like having spare parts left over.

 

[stork55]

If I remember right,it does go on the driveshaft with the flat side down and there should be a thin rubber sleeve that also slides over the driveshat to protect the splines.Likely it fell off when you removed the lower unit.

 

[Dwayn66]

If I remember right,it does go on the driveshaft with the flat side down and there should be a thin rubber sleeve that also slides over the driveshat to protect the splines.Likely it fell off when you removed the lower unit.

Thank you so much for your reply, attatched is picture after I put it on shaft, it stops right at spot in picture, I must have watched over 40-50 videos of replacing the pump on 40hp-115hp from 1996-2015 and not a single 1 shows this, also every site that has parts for my motor does not show this part, just hard to believe only my engine out of 1000's has it.