88 Merc 20hp Waterpump Seal question

[ugmold]

Hi folks,

Had a impeller go in my 20hp 1988 Merc, bought a kit, lower unit came apart ok, but under the pump housing the drive shaft seals looked nasty, I dug around a bit and the top seal (I think there is 2) was wasted, spring sticking up. I got it out fairly cleanly. Looks like the one below is ok, so I'm leaving it for now.

My concern is the housing around the seal looks pretty bad, check the photos, is there a work around, sealant?

Thanks much for looking,

-Ugmold

 

[aussieflash]

Re: 88 Merc 20hp Waterpump Seal question

Check for water in lower unit.If all good leave the lower seal alone.Dont know if that sought of damage is repairable in that location.I would replace seal and clean surface up as best you can.
Might be time to start looking for a lower unit if water is found in gear oil.

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

Good advice. Thanks.

 

[oldman570]

Re: 88 Merc 20hp Waterpump Seal question

Check for water in lower unit.If all good leave the lower seal alone.Dont know if that sought of damage is repairable in that location.I would replace seal and clean surface up as best you can.
Might be time to start looking for a lower unit if water is found in gear oil.

You should use silacon sealer when replacing the upper seal and that should help with sealing to outer edges of the seal as it will get pushed off as the seal is put into place. A thin coating of sealer on the outside of the seal should be all that is needed. Wipe off any sealer above the seal after install .
Oldman570

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

You should use silacon sealer when replacing the upper seal and that should help with sealing to outer edges of the seal as it will get pushed off as the seal is put into place. A thin coating of sealer on the outside of the seal should be all that is needed. Wipe off any sealer above the seal after install .
Oldman570

That makes me feel a little better about it. Do I need to let it set up for a time?
Thanks-Ug

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

Drained the lower unit tonight, pretty decent, a little gray, nothing creamy, oil was pretty dark, can't recall when I changed it, or if I changed it, I've had it for four years before putting it on the boat.

I hope the new seal will make it tighter.

-Ugmold

 

[oldman570]

Re: 88 Merc 20hp Waterpump Seal question

It is best if the silacon sealer set up for 12 hrs or so before putting the LU back on the motor, or a day berfore running the motor.
Oldman570

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

Got the seal in pretty cleanly, scrapped off a lot of salt/corrosion, only a small area needed fill from the silicon, thanks oldman570.

I was putting it back together and didn't feel comfortable with which way the impeller goes in, and I can't count on the old one. This image implies they point in a clockwise direction: http://www.**********/images/diagrams/Merc2/COMMON//21824.png



Anybody know. my manual says nothing, and actually has been way off on this procedure as it covers too many years and models.

Also on that image there is a small washer #19 very top part. I don't have one, or it was lost pulling apart, neccasary?


Thanks,
-Ugmold

 

[oldman570]

Re: 88 Merc 20hp Waterpump Seal question

The impeller vains should be pointing counterclockwise when viewed from the top, as the driveshaft turns clockwise. The rubber O ring on thr top of the pump housing acts as a water slinger an helps keep any water from being sprayed up the DS and into the splined aera of the motor. On older motors the DS is not stainless and needs to have the splines that go into the powerhead greased to prevent corrosion from locking them together. A small amount on the splines is all that is needed, and none on the top of the shaft or it will cause a preload on the crankshaft and motor failure. I use a light touch of grease on the back of impeller key to help hold it inplace when putting the impeller on the DS. Turning the DS clockwise often helps when placing the upper pump housing over the impeller and the viens will be in the correct direction. JMO
Oldman570

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

Thanks oldman570. I got it together, light grease. I have left 2 o-rings and 2 yellow (specialized washers) looks like they go on the studs, seem to fit well in the holes.

I am also still wondering about that washer I mentioned above, I was careful when I seperated the lower end and doubt I lost it, probably was either lost by the PO, or doesn't have one. It seems my engine doesn't seem to be exact to any schematic or procedure I have seen.
-Thanks again! Ugmold

 

[ugmold]

Re: 88 Merc 20hp Waterpump Seal question

I figured out the tilt pin release: http://forums.iboats.com/showthread.php?t=569723

Put it all back together, ran it, have a gas leak at the fuel filter, missing o-ring, dammit. I ran it, and water came out, but since the engine was running bad due to the leak, I have not been able see if the water pump is working correctly.

-Ugmold