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Steps For Pressure Testing Lower Unit?

S

sturgeon_general

Member
I have water in my 1981,Evinrude,25hp,#E25RCIM, lower unit oil.I have been using it still what can I expect in damage and can I get away with one or more trips before fixing?It appears to be leaking a little around the propeller.I don't want to mess around with the gears in lower unit,does replacing prop seals involve removing these gears and special OMC tools?I want to pressure test the lower unit to make sure where water is leaking in but want the info on procedure steps,any advice or info would be greatly appreciated,Thank You,"The SturgeonGeneral".
 
If you change the oil regularly, a little water in it is not going to cause any catastrophic failure. It just reduces the lubrication somewhat depending on how much is in there. The first thing I would do is change the seal washers on the vent and drain plugs, since this is usually the culprit for most LU leaks. Run it for a while. After it has sat for a few days (to allow time for any water to seperate from the oil and move to the bottom of the LU), unscrew the lower plug and see if any water comes out.

What I have done in the past to find a leak is to drain the LU oil, hook up a compresser to the plastic hose of a LU oil pump that can screw into the plug hole of a LU. Put no more then 10psi on it and drop it into the water and look for bubbles. They recommend a vacuum test along with this pressure test since sometimes water gets in but oil does not always leak out and perhaps vice versa. For a proper pressure and vacuum test you would need to see a mechanic that is set up for it.

I can't tell you how to remove the prope seal on your unit but I wouldn't just start removing seals until I knew where the leak was. The oil out of the prop could very well just be unburnt exhaust oil, which is normal.
 
It is fairly easy to install a seal kit.-------------No special tools required except for the shift rod o-ring and even that can be replaced without removing the bushing !!-------------Would be cheaper than risking damage to the gears !!!
 
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