Please explain ......what seal is leaking

oldboat1

Fleet Admiral
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Apr 3, 2002
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It's pretty easy to rig a pressure tester either to troubleshoot or to check repairs. I use a foot pump, and test with the lower unit submersed in a tub (l.u. removed from motor). Light pressure, maybe 8 lbs or so. Watch for bubbles to identify leaks.
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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thanks to all and Raceone ...Ive ordered parts...will let you know.
 

dthx

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Apr 13, 2016
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#25E76E Johnson 1976 25 HP
Has anyone replaced the prop shaft (lip) seal in the gearcase (head assembly) ?
The seal isnt called out in the parts schematic....
I looked isiden the head assy and it;s in there....looks like you have to take the assy apart....but is the seal available by itself or am I to buy the whole assy ($154.00)
Anyone know..?
BTW...it's all back together (lower unit)....and I used some of my high dollar sealant,,,,that $17.00 per tube stuff....the stuff that will only come off with MEKThanks to all.
 

racerone

Supreme Mariner
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Dec 28, 2013
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The seal in that assembly is easy to replace.---No need to buy the whole thing.----Remove seal.----Take measurements of seal.----Find a replacement and install.
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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Well....I've replaced the shift rod seal and bushing and little washer below the oring.
I didnt replace the drive shaft seal.
It still leaked.
So I took it all apart again and I'm getting ready to replace the shift rod bushing, O-ring, and little flat washer (domed side towards the o-ring).
I couldnt find anything wrong with anything....there were a couple of screatches but nothing bad.
Except....
The service manual (after I read it in detail) says to put some 3M sealant on the casting under the water pump plate. Not on the impeller housing but under the little silver plate....
After looking closely I could see some gasket sealant material that was on the water pump casting.....
I've never done that.
So...I'm going to put it all back together and do that too.
Question:
Why does the Drive Shaft Seal have it's seal lips facing away from the water pump area.....?
It seems that the seal's lips should face the other way.....
I'm just asking because I know that it is correct to insert it with it'd lips toward the gearcase.
Any thought from anyone?
 

AlTn

Commander
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Mar 9, 2010
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seal under the w/p is to keep the oil in the gearcase...concerning the shift rod oring and bushing..tap down around the bushing while moving the shift rod up and down to find a point that you have the oring tight but not too tight..it's not difficult to get it so tight that it really binds the shift rod to the point you'll have difficulty pushing and pulling it
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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Thanks everyone.
Regarding the shift rod seal and bushing.
There are 4 parts to this job.
The shift rod
A flat black washer that is flat on one side and slightly domed on the other.
A brass bushing which the shift rod goes thru
A little fat o-ring that fits tightly into the bottom of the bushing.

I put the flat washer in with the dome facing the bushing and the flat against the casting
I insert the 0-ring into the bushing...it fits from side to side and I have to push it to get it in the bushing.
However, the o-ring does not completely fill the cavity in the bushing.
It fits side to side but is not thick enough to reach the bottom of the bushing.

If and when I drive the bushing in and bottom it out, there will be a space between the 0-ring and domed washer.

I appears that the o-ring will be able to "float"up and down in the bushing.

I won't be able to increase friction on the o-ring by driving the bushing down because the bushing is longer than the o-ring is thick and there will be a space between the o-ring and the flat washer.

I'd like the dome on the washer to go into the bushing and sit against the o-ring but it won't.

I have put this together and put some 3M sealant around the bushing as well before I drove it in.
The shift rod moves up and down easily.
I'm not sure how to judge how easily it should move.

Question to someone that has done this before....
Am I doing this right?
OR....could I have the wrong bushing or washer or o-ring?
I have 3 of these bushings and they are all the same.
I have also ordered 3 or 4 of the washers and o-rings and they are all the same.
 

AlTn

Commander
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Mar 9, 2010
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the bushing/seal set up I was referencing is different than what you have...if your bushing is bottomed out in the casting then that's it, your oring/seal is as tight as it needs to be to seal the shift rod...your old oring was probably getting brittle and deformed so it wasn't sealing as it should
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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147
I cant understand it.
Still leaking after replacing the the shift rod bushing,the shift rod o-ring, and flat washer.
3M sealant around the shift rod bushing,
New drive shaft seal.
Still leaking out of weep hole common to the top of the shift rod bushing and the drive shaft seal.
I'll have to takr it all apart again.
This time I'll have to find some way to pressure test it.
 

lindy46

Captain
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Nov 27, 2008
Messages
3,886
Are you sure you have a problem? There are weep holes in the exhaust housing/lower unit designed to drain unburnt gas/fuel and water. There are no weep holes into the gearcase itself. It is a closed system. Maybe what you're seeing is just unburnt gas/oil draining as it is designed to. Unless you have a crack in the casting itself.
 

AlTn

Commander
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Mar 9, 2010
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2,813
are you seeing gearcase oil leaking from a weep hole whose purpose is to drain water and fuel mix from the lower unit?...as Lindy notes the gearcase itself is a closed system, or should be at any rate
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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147
When I take the lower unit off and look down into it...I can see the water pump with the drive shaft sticking out of it.
I can also see the shift rod bushing with the shift rod sticking out of it.
Yes the gear case is below all that with gearcase lube oil inside it.
There is a weep hole near the shift rod bushing that is meant to drain water out of the casting gullies to keep the water from freezing..
When the lower unit is put back on the engine....and I run the engine for a while.....and take it out of the water......that little weep hole leaks oil mixed with water.
I'm sure its not soot and water.
I'm going to take the unit off again and pressure test it.
I haven't done that yet..
I should be able to fix this.....
I'm pretty sure I've replaced all the seals correctly.
Thanks everyone....
 

lindy46

Captain
Joined
Nov 27, 2008
Messages
3,886
There is a weep hole near the shift rod bushing that is meant to drain water out of the casting gullies to keep the water from freezing..
When the lower unit is put back on the engine....and I run the engine for a while.....and take it out of the water......that little weep hole leaks oil mixed with water.
I'm sure its not soot and water.

Perfectly normal - that is unburnt fuel/oil mixed with water.
 

dthx

Petty Officer 2nd Class
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Apr 13, 2016
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147
These are the pictures of my lower unit......
Something is wrong....
I either dont have the right o-ring or something ......
Looking forward to the pressure test ...but then what?
this is not rocket science.
Any comments on my pics or thoughts?
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
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9,598
may be differing opinions, but I don't think it's gear oil. As I mentioned earlier, smell it. Gear oil will have a sulfur smell, not a gas smell.

You may be running cold -- thermostat issue, maybe.

But do the pressure test to satisfy curiosity.
 
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