[Public-List] Rear Oil Seal Replacement on Atomic 4

[Clay Pass]

Here's a little write up I did explaining my process for rear oil seal
replacement on the Atomic 4 for those that have pesky oil leaks from
"somewhere in the back of the engine".  I thought it might be useful
information.

So, I had promised to post about the "great rear oil seal replacement job"
on my Atomic 4.  I finally feel like I’ve beaten this oil leak gremlin to
be able to declare victory.  First a recap … oil was leaking from the rear
of the engine, but only while running AND in gear.  I visually eliminated
the oil pan gasket and two other common sources of leaks, the valve cover
and oil pressure regulator.  Both of these areas were dry and there was no
trickle back found on the cast iron mounting flange of the engine leading
to the rear.  Also the volume of oil leak was A LOT while in gear, so the
obvious source was the seal on the output shaft.  Hopefully you have a
large access panel in your cockpit to reach this area, because this would
be a difficult if not impossible task to do otherwise without pulling the
engine.  Gaining access, you first unbolt the propeller shaft from the
output coupling and slide the shaft aft as far as it can go.  I first
marked across the flange/coupler with a sharpie because I wanted to
reassemble with the exact same alignment, just in case.  Sliding the shaft
back was a little difficult because my cutlass bearing and packing were
recently replaced so it was a little tight.  I used a little grease on the
shaft to help and a pry bar to help move things aft.  Luckily, no leaks
resulted as this was done in the water and what I thought was going to be a
couple of hour job turned into several weeks!  Who knew?  L.  Also remember
to move the tiller fully to one side to allow enough room for the propeller
to slide aft without hitting the rudder.

When fully aft, there was barely enough room to get a 1-1/8” socket and ½”
breaker bar on the output shaft spindle nut.  I threaded a couple of the
bolts back into the output coupling and put a hefty screwdriver across them
against the hull to keep the shaft from turning while I broke the spindle
nut loose.  Remember to bend down the retaining ear of the “lock washer”
underneath before trying to remove this nut.  This actually came off pretty
easily.  Remove the washer underneath.

Next the fun part, I used some slightly longer 3/8” fine thread bolts
threaded through the coupler holes until they pushed on the flange casting
underneath.  Tightening each successively pushed the coupler off the shaft
after a hour or two of tedious tightening with a box end wrench, because
there wasn’t room enough for a socket and ratchet (boo!).   The bolts I had
weren’t quite long enough to push it all the way off, so at the last little
bit I had to back them out and put a screwdriver or some spacer underneath
to be able to push a little further.

With the coupler removed, the seal is right there, exposed in the opening
of the mounting flange.  Logic would suggest that a simple pry with a
screwdriver would pop it right out.  Having a spare engine at home in the
garage proved this point.  The attached picture shows how I practiced this
concept at home and sure enough, the seal popped right out without having
to remove the flange (seal on the left).  For this reason, I did not order
new gaskets for the flange because WHY remove it???    Well, as one should
have known, with the real engine in the boat, it seems like someone must
have welded the seal in place and no amount of prying or knuckle banging
was going to budge it.  How could such a tiny seal hang on so tight?  I had
bought the replacement seal that I had planned to just tap right in, but no
gaskets.  The replacement seal is a National p/n 473227.  There may be
other equivalent parts from other vendors being used.  So I ended up having
to remove the rear flange anyway to take home to a vise to pound/pry out
the offending seal.  The result is the seal shown on the right in the
picture.  It looks like it was removed with a stick of dynamite!  The
gasket you need is also shown (you need 2 of these).  Be sure to inspect
your coupler for wear at the interface with the seal.  The old seal,
instead of being flexible, had aged to hard plastic and will have a
tendency to wear a groove into the coupler.  If the groove is noticeable
then go ahead and replace the coupler.  These are available at Moyer’s for
about the same price as buying his “repair sleeve”.  The delta is only
about $4 so why buy the sleeve?  Anyway, I decided mine was ok and I reused
it.

Unfortunately, I now had to order 2 of these flange gaskets and that
resulted in the 2-3 week down time (first place I ordered them didn't have
them in stock and put them on backorder).  Buy them from Moyer’s, they have
these in stock.  Lesson learned!  If you can remove the seal without
removing the flange then do that and you’ll be  way ahead.  Also consider
when you remove the flange it will immediately dump your oil so be prepared
to catch this mess in a pan or something to keep it out of your bilge!  Also,
before removing the flange, I marked its alignment with the engine block
with a sharpie so I wouldn’t have to guess upon reassembly since it looked
symmetrical.

So reassembly … obviously clean all surfaces of old gasket material and
apply the new gaskets.  The rear flange actually comes apart in two pieces
exposing a bearing in the inner plate.  That’s why you need 2 identical
gaskets.  I tapped the new seal in place and lightly greased the bearing
just because I could.

Back at the boat now.  Having been forewarned.  I lightly wrapped some
electrical tape around the exposed output shaft and key to cover sharp
edges and protect from nicking the new seal when fumbling the flange
assembly back on the engine (clean any old gasket material from engine too).
The output shaft is loose and “floppy” when it is unsupported, so use one
hand to hold it in position while guiding the flange assembly into position.
After installation, remove your electrical tape.  Next the fun part and
lesson learned.  Reinstalling the output coupling on the shaft.  First use
plenty of grease to make this as easy as possible.  Grease both the shaft,
the bearing inner race within the rear flange and both the inner and outer
mating surfaces of the output coupling.  Key to remember is that the
coupler is both pressed onto the shaft on its inner surface as well as the
bearing and oil seal on its outer surface, so grease both.  I used the
tapping method with a hammer to get the coupler started on the shaft far
enough to finally be able to thread the spindle nut and then by tightening
the spindle nut until the coupler was fully seated against its stop.  So
here’s the trick … it will seem that progress is being made a little tap at
a time while standing on your head and with barely enough room to swing a
hammer when it just won’t go any further and stops just short of being able
to thread the spindle nut on.  The secret is, remember the ”floppy” output
shaft?  You have to support the shaft, slightly wiggling with one hand, to
center the shaft in the assembly while you are tapping the coupler with the
hammer using the other hand.  With much aggressive “tapping” the coupler
will slowly begin to move again.  Once the threads are exposed and you can
get your spindle nut on again, the rest is easy.  Use something to keep the
shaft from turning and use your 1-1/8” socket and breaker bar to firmly
seat the coupler.  Then remove the spindle nut and install the “lock”
washer underneath.  Reinstall the spindle nut and bend up an “ear” on the
lock washer to hold in place.  Reattach the propeller shaft using the
alignment marks.  Luckily, the shaft pulled forward by hand with a little
twisting and pulling perhaps assisted by the grease I had earlier put on
the shaft.  The rest was without issue.

Remember to refill the oil.  Of course, like I like to overtighten stuff, I
also like to overfill things.  Don’t do that.  During the trial run I had
excess oil overflowing from the oil fill spout area.  My fill spout is on
the rear of the engine and is probably vulnerable to over-fill issues
because of the tilt of the engine.  That is another area to check when you
have oil leak/spillage at the rear of the engine.  However, with all that
cleaned up, I can happily report that I have no more oil leaks!  What a
blessed day this is!  J



Clay Pass
#449 Seeing Deep