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i have a wn7a powermatic 12. the powerhead runs great, but the foot is getting water in it. i have replaced the seal behind the prop it now holds oil in so that part is good. i am almost certain it is coming from the seal under the water pump. i have removed the stainless insert and bottom piece that hold the impellar , there is another piece that appears to be cast alluminum and is held in by a pin driven between that piece and the housing. does anyone have ideas to get it out without damaging it?
is there any thing else that could let water in? besides a crack?

Re: seals


Are you using gear oil or Lubriplate grease in that lower unit? The Mercs of that vintage are notorious for their bad lower unit seals, and though I wouldn't necessarily discourage a seal replacement job, many recommend using the Lubriplate 105 grease in the lower unit, as it will offer better protection since a certain amount of water intrusion is pretty much a given on those outboards. I just acquired a Mark 15 and 20 and will be using Lurbiplate in both. However, in my 1965 Merc 39, I use conventional gear oil (80W-90).

Just my $0.02. Other may have more experience and better perspectives to offer.


Re: seals

yes, i am using standard marine grade gear oil.i will consider grease but the motor has been in the family since almost new i would wrather put the seal in (it leaks pretty bad). do i have to completely disassemle the lower unit and remove drive shaft? u know a good source for a manual?

Re: seals

Seals are inexpensive and usually can be
cross referenced by part numnber to a C/R part number.
Seals are selected by diameter of shaft, diameter of
recess seal fits into and height.
The crucial question is...Will a new seal seal?
Shaft surface in area where lip of seal rides has to
be smooth and concentric.
It is not uncommon to find shaft surface too rough
to allow a new seal to function properly.
If a good usable shaft is not an option then switching to grease or frequently flushing and
changing lower unit oil are possile options.
Sometimes a shaft is grooved only where the lip of seal rides...use of a taller seal or two seals may allow lip to ride on a good surface. Using an epoxy filler (such as JB Weld) on a rough shaft has been mentioned elsewhere...would it work and hold up over long term?
One choice you do not have is taking it to a dealer
as very few will work on older outboards, shop
time $85 to $100 per hour for those that do...and
they would probably lose money.