pressure test question

[locknut550]

ive got a 1979 mercury 7.5 hp outboard. i changed the lower unit seals but im still getting some water in the lower unit not a whole lot but enough to turn the oil milky only after 1 day on the lake .i cant figure out where its coming from .ive heard about doing a pressure test. i own a air compressor. can i do a pressure test with that or do you need some special equipment?

 

[Paul Moir]

Re: pressure test question

You must ensure that you do not pressurize the unit beyond 5psi or you will blow out the seals. So an air compressor is really overkill. A hand bicycle pump and an old tire valve stem carved to fit a fill/drain screw hole work well. Submerge the lower unit and see where bubbles come out.<br /><br />Be gentle with the bicycle pump even. You're aiming to only put about 5 pounds of pressure on the handle of a typical one. (1.5" diameter pump, 5lbs=~3psi)<br /><br />Good luck!