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Water in lower unit

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dcbullington

Contributing Member
I have a 25 hp (serial # range OB238464) mercury that has got some water in the lower unit. I realize that this is not uncommon and probably requires a pressure test to
determine which seal/seals are the culprit. My question is what is the best way to do this and does it require any special tools? I have an air compressor, can I use air to pressurize the lower unit or does it have to be gear oil?

Thanks,

Dave Bullington
St. Charles, MO
 
The drain screw is a 3/8"-nc thread --------------so make up a fitting to use a shreader valve and a bycycle pump instead of compressor ( safety concern ) to put a few lbs pressure in there.----Oil drained of course.
 
Many foreign built motors have oilseals that have rubber on the OD as well as the lips on the shaft.-----------Now this is not bad when the stuff is " all new " , but over time they loose their grip in the housing and shift ( particularly on double seals with water in between them )------------In freezing climates they are a risk to the lower unit.-------------People who have not owned older ( well made ) motors may not be aware of this. Then again today people will say " it's 10 years old , time to buy a new one anyway "
 
Thanks racerone.....I have a regulator on the compressor and can bring the pressure down below 5 psi...would that be OK? Also, just curious, what do you consider an "older" motor?

Dave
 
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