Re: [omc-boats] Impeller

On Tue, 27 Jun 2006, Gregory B. Fell wrote:
> 1. My original 1969 OMC repair manual does not cover impeller
> replacement. Is it a DIY repair? I'm pretty competent -- not like some
> of the others on this board, though.
> 2. Would the Seloc manual be better than the original OMC? Does it
> cover this repair?

I originally wrote this just to George, but I figured others in
the list might be interested and I hate to think I'll type it again
at some point. It's fairly easy and I'd recommend using the Seloc manual
over the original OEM manual. I think it can actually be done with the
drive still in the boat and without draining any oil, but I'm not
sure of this - I did it as part of a larger overhaul and had everything
taken off and apart.

I've put some photos of the process on my website.
This is what you'll see when the upper and lower unit are separated.
  http://homepages.cae.wisc.edu/~brodskye/boat/parts/out_upper.jpg
  http://homepages.cae.wisc.edu/~brodskye/boat/parts/out_lower.jpg
The top of the lower unit bolts to the top of the upper unit with the
5-6 small bolts visible on the top of the drive. Be sure to clean
the threads and use thread-lube during reassembly - I broke one the
bolts on mine.

The upper unit is shown upside down here. The "water pump housing cover"
is the plate visible on "top." You remove those four bolts to pull
the pump housing cover. Those four bolts also hold in the "spacer".

The spacer was stuck in pretty well on my unit and difficult to
remove, which was good, because I don't think you need to remove it. It
might have an oil seal on top - I can't remember how the oil is retained in
the upper unit, but be careful about spilling the oil if you do remove it.
I think there's another seal on top of it, where the shaft comes through,
but I don't remember that part so well. If you do remove the spacer, don't
lose the metal shims which are on top of it.

Once you've removed the cover, the pump housing will be visible (you can
actually see a bit of it (in upper.jpg) in the gap between the upper unit
main body and the water pump housing cover). Pull out the housing - I
think the pump shaft and everything should come with it. Don't lose the
woodruff key (though you are supposed to replace it). If it's been a while,
I'd recommend replacing at a minimum the impeller and housing, though in
retrospect I wish I had replaced the cover plate, seals, and key as well.
My housing was badly damaged (had a big dent in it - most likely from
freezing). Squirt some dish soap in before reassembly to help lubricate
the pump the first time it spins. I was paranoid and made really sure the
pump blades were bent the right way as well, though I'm not sure if that
mattered.

Also, while it's apart, look at the top splines for the water pump shaft:
  http://homepages.cae.wisc.edu/~brodskye/boat/parts/img_3662.jpg
Trial-fit it back into the upper unit and feel for sloppiness. I was told
that that water pump shaft upper spline wears faster than the upper
unit shaft and will eventually get so loose it can slip and damage the
upper unit shaft. Water pump shafts can be had for under $100 (be sure
to get the right length) and are significantly cheaper than upper unit
shafts and gears.

Ethan

-- 
<A HREF="http://www.engr.wisc.edu/~brodskye/"> Ethan Brodsky </A>
UW FutureCar Team Paradigm: Two-Year FutureCar Challenge Winner
UW-Madison Clean Snowmobile Team: Winner of the 2004 SAE CSC
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