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Pressure testing lower unit....hissing but no bubbles with soapy water

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PhilSch

Regular Contributor
When pressurized with 10-15 psi hissing occurs but no bubbles appear after spraying soapy water on prop shaft seal, shift rod or water pump seal. The hissing sound is considerably louder coming from the exhaust cavity. Is there any other seals the leaking can come from besides the three areas mentioned?
 
Each screw on the propshaft bearing housing has an 0-ring.----There is a big o-ring way inside on the propshaft bearing carrier.-----O-ring on driveshaft bearing carrier,-----Gasket on shift rod cover.----Plus perhaps a crack in the housing somewhere.
 
Ok, so I dunked the unit under water and applied pressure. The bubbles are coming only from the exhaust cavity, just like it sounded. Nothing from the external seals. I could not find any cracks upon close inspection of the housing.

I am sure it needs to come apart and am willing to do that but I hate to invest a bunch of money in special tools that I may never use again. What if I just change the oil once or twice a season? It will not be run in salt water.
 
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Not sure what you have for an engine but I resealed my 225 Evinrude lower unit last year and the only tool "special" tool I needed was a gear puller that I happened to have. I think auto zone or one of those places will lend one for free. Oh, and to install the seal that gets put in backwards i had to cut the threads off a black iron pipe nipple to get the correct size tool to put the seal in. The only other tip I have is count how many turns to get the shift rod out so you can get it back to where it started from. I also used a piece of wood that i cut to clear the shift rod housing so i could confirm the shift rod was where it was supposed to be, it was.
 
Thanks I will have to view some you tube videos on the process. I have a number of gear pullers and am also adept at making tools when possible as I have both a mill and lathe.

One question that came to mine...could the lower unit be cracked internally?
 
It should be fairly easy to see where the leak is with soapy water.----No point in resealing if housing is cracked.------Or bring it to an outboard shop and have them show you in minutes where the leak is !!
 
racerone said:
It should be fairly easy to see where the leak is with soapy water.----No point in resealing if housing is cracked.------Or bring it to an outboard shop and have them show you in minutes where the leak is !!
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I did apply soapy water and got no bubbles from any of the seals but could hear a very distinct hissing from exhaust cavity. Per Baddog's suggestion I submerged the unit and there were lots of bubbles coming from the exhaust cavity
 
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