Lower Unit Leak Test

Looking for information to pressure/vacuum test for leaks on 2003 Mercury 135HP lower unit. Gear oil appears milky, so I suspect a leak, but I would like to test to determine which seal is leaking.

If you pull the plug on a recently run lower unit, the fluid always looks that way. Let it sit overnight and take another look. Be especially watchful for water coming out first.

Jeff

Pressure test only after its been fully drained, otherwise most often the grease or grease/water mixture will seal the leak enough to fool you. Besides that, its leaking water as its turning and running, shifting, etc...impossible to recreate while under pressure test. I pump to 15psi with an adapter that I made for my Stant radiator tester with hand pump. I also like to have the housing temperature at least 70 degrees when I test. Try turning prop shaft, shifting, and wiggling driveshaft. This will kind of duplicate operating conditions. Water pumps may need to be removed for effective examination/test of the driveshaft seal. Dish soap mixed with water works pretty well. Didn't watch the youtube but will now. Thanks joeanna.

Okay, my take on this video. The mechanic never moved around or turned the shafts to encourage leaks. Also I like to run 13 to even 15 psi. I tolerate no loss of pressure at all. A 2 pound drop is not acceptable. Why? Everything will be more likely to leak under operation. I don't claim to be an expert but here is a 135 Optimax that I rebuilt late last summer for a guy that backed into a rock pile, wiping out the prop and bending the shaft .035. Used skeg was cut off a donor unit and sent to me from Tim's Outboard in Hackensack MN. Welded using my Miller MIG 4043 filler, straight argon. Paint is automotive epoxy, base/clear.