Johnson 100hp leaking crank case oil

SideW@ys

Cadet
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May 18, 2009
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This is my first boat. So far I've had to fix many things and something new just came up. My outboard is leaking crank case oil where the prop is connected to the lower unit. Is this a matter of tightening a bolt, or do I also need to replace a bushing or gasket of some sort? Thanks for you help! the engine is a 74 johsnon 100hp WTL
 

vegasphotoman

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Jul 13, 2009
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1,411
Re: Johnson 100hp leaking crank case oil

check your Private messages Sideways.....sent ya something

sounds like you need a new seal at the output shaft.......

shouldnt be too bad of a fix and not too expensive
Good luck
 

Vic.S

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May 4, 2004
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4,690
Re: Johnson 100hp leaking crank case oil

I cannot find such a beast as a 1974 100 hp. However it's a 2 stroke surely and does not have "crankcase oil".

What you are probably seeing is unburnt oil from the fuel. Thats normal for a two stroke.

But if you have gearcase oil leaking then you do have a seal gone. If you suspect it's gear oil check the gearcase oil for signs of water ... milkiness = water.

Read THIS ITEM on the Engine FAQs board about "Oil leaking around the lower unit"

Tell us the model number and we will tell you the year and HP
 

tx1961whaler

Vice Admiral
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May 31, 2008
Messages
5,197
Re: Johnson 100hp leaking crank case oil

The propeller slides on and attaches to the prop shaft. If it is leaking around the prop shaft, then the seal needs to be replaced. A common cause of this is fishing line that gets wrapped around the shaft and mangles the seal.
 

SideW@ys

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May 18, 2009
Messages
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Re: Johnson 100hp leaking gear case oil

Re: Johnson 100hp leaking gear case oil

Thanks for the replies. You're right vic, It's the gearcase oil. Also I was wrong about the year, it's an 84 not a 74. It's been a couple of months since I've had to get a part for it. Here is a link to the evinrude/johnson websit. Which part would I most likely need to purchase? I can't tell from the diagram.

Thanks!
 

Vic.S

Rear Admiral
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May 4, 2004
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Re: Johnson 100hp leaking crank case oil

1984 thats better!

Here is a link to the evinrude/johnson websit
Errm ??

Here IS a link to the parts diagram http://shop2.evinrude.com/Scripts/I...79\18.TIF&ilSC=33&ilIV=0&ilBR=0&ilIF=P&ilRE=8

and one to the parts list http://shop2.evinrude.com/Ext/PartList.aspx?assem=44640 at Shop.evinrude.com


The only way to be sure about gear case leaks is to do a pressure/vacuum test but the most likely seal is the prop shaft seal (a pair actually) #27 in the diagram (Note how they fit back to back) They are vulnerable to damage from fishing line etc as said above
You'll need the carrier O ring as well #17

The drive shaft seals #50 and 51 could also be leaking but you probably see oil leaking from the water intakes

Even the grommet, o ring or gasket associated with the shift rod could be leaking.

If the water pump impeller is due for change it might be worth doing at least the drivesft seals at the same time (Theres an O ring on the housing there too #5)
 

SideW@ys

Cadet
Joined
May 18, 2009
Messages
20
Re: Johnson 100hp leaking crank case oil

Thanks for your help guys. I just wanted to let you know how everything turned out. Vic was right on the money. I bought a new prop shaft seal for ten bucks hoping that would solve the problem because it seemed like the best bet. Sure enough, when I pulled the prop off there was a pretty good size bundle of fishing line wrapped around the seal. The seal was so destroyed it was unrecognizable to the replacement part I was trying to compare it too. Thanks to you guys I was able to take care of it for ten bucks in about ten minutes. Thanks a bunch. I'm sure I'll be back.
 
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