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New prop shaft seal still leaks.

I replaced the prop shaft seal,as it had leaked,and bearing when I was putting together one 7.5 from two,a '75 and '76. After adjusting the idle in a barrel,I have one inch oil spot under the leg in the garage. This is the second time I've had this. This doesn't seem normal. I didn't feel a groove on the shaft when I installed it. I put the lips to the inside and filled them with grease. I didn't have new fiber washers for the fill and vent screws so I used some white teflon sealant,Locktite # 597. What did I do wrong? thx
 
Are you sure it's lower unit oil and not just burnt/unburnt 2 cycle oil that made it's way through the exhaust?

If the oil spot is "blackish" and smells burnt I suspect it's two stroke oil. If it's honey coloured (or whatever colour lower unit oil you used - most are honey but could also be green) then maybe you still have a seal leak.

If you really suspect it's a seal, spend the few bucks to have it pressure tested - no sense pulling the bearing carrier again only to find out that it was simply a fill or vent plug seal....
 
Thank you,I think you nailed it.It was black and oily and not sticky like gear oil.That also means the 4.5 I use on the canoe doesn't need it's seal changed,either.I used Quicksilver gear oil. Another oil seal was hard to find at the bearing supply,it's 5/16" deep instead of the common 1/4",so it was a dealership item. Thanks again.
 
I had the same problem with a used 25 HP Merc. I've changed the lower unit oil but have not yet check it for water intrusion since changing. Did not have the pool of black oil on the garage floor after last trip to the lake. It only happened when I tanked the motor and ran it at low RPM for a while.
 
Two strokes are pretty inefficient.

A good percentage of the gas/oil mix passes right through the cylinder without ever getting burned because both the intake and exhaust ports are (open) when the piston is (down) on it's induction stroke - you don't have valves to keep the cylinder "closed" so some gas/oil goes right into the exhaust (where some sticks to the wall of the exhaust housing).

Secondly, when the cylinder does fire it burns almost all of the gas and "most" of the oil from the mixture, but by it's very nature you don't want to burn up 100% of the oil since it is needed to help keep things lubed up - but again, all that (crap) goes into the exhaust - some sticking to the side.

Normally when you are "underway" that all ends up in the lake as it works it's way out the exhaust - any residual "drips" out on the drive home with the boat on the trailer.

So some people only notice that "oil drip" if they run the motor on a flushing device or in a pail of water (or if they drive home fast and the motor still has "cooties" leaking out the exhaust) and falsely assume it's a gear oil issue.

It is completely normal - that gunk has to go somewhere and since most 2 strokes built in the past 30-40 years have a "thru-hub" exhaust (exits out through the propeller hub), it drips from there which is exactly where either a bearing carrier seal leak or propshaft seal leak would show up....
 
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