1992 Force 120 Water Pump replacement

[Mytox]

I'm replacing the water pump on my '92 120 Force, and purchased the kit FK1204-1. The kit contained a black rubber washer the same ID as the shaft (basically an o-ring with flat edges/sides). This appears to be a seal for the top of the water pump, although I'm not sure where it goes as the old pump did not contain this part. Any suggestions are appreciated. The ice just cleared out of the bay where I launch my boat so the clock's ticking.

 

[pnwboat]

I know exactly what you're talking about. I've often wondered myself. Doesn't look like it does anything. I don't know for sure, but on the lower units that I've done, I just slide it down the drive shaft and let it sit on top of the water pump. I believe it's item #41 in the diagram.

http://www.crowleymarine.com/mercury-outboard/parts/1470_250.cfm

 

[Mytox]

Thanks for the reply. Looks like #41 is the part, and it looks like it's installed as you describe above, although what it accomplishes is a bit of a mystery. It would be spinning around on the drive-shaft above the stationary pump housing, not really sealing anything (does some water escape from the top of the pump when it's operating? You'd almost think some would because it's not really sealed where the shaft goes through the housing, at least it doesn't appear to be).

Randy

 

[Mytox]

Yea. Think I found the answer. It's not an o-ring, but a centrifugal 'slinger' as described by a merc mechanic:

"Well, the slinger is just that, a slinger. It's not a "secondary" seal. The slinger is installed so it is touching the top of the water pump housing. The pump housing is about 1/16th inch larger than the driveshaft and this gap makes a nice "cup" to catch undesireable crap. The intent of the slinger is to "sling" sand, gas/oil (undesireable crap), or anything else that might run down the driveshaft and enter the top of the water pump housing making the impeller last just a little longer"

 

[Michael Lang]

Thank you for you post Mytox I bought a used 1991 70 ho force motor and could not find any reason for this flat black rubber washer on my driveshaft when I pulled the lower unit, after reading your post I did some research and found that my type of water pump (no insert) should not have this washer sitting on top of my water pump housing....Thanks again