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Gear Case Pressure Test

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6tring

Contributing Member
Johnson 1965 6 hp. Foamy gear oil at end of season. I would like to do a pressure test to find where the leak is. I did replace the bearing seal and gear case seal. Still leaked. At this time I would think that the shift rod o ring is the suspect. I put together a pressure tester I cobbled together from components from the Home Depot and the yellow fitting is from a gear oil pump kit. Having never done a pressure test before my question is should it be done with oil in the case or drained. I can submerge the lower unit under water and try to detect air bubbles. What is a good pressure that should be held. The tester goes to #15 and I will use a hand pump to pressurize.
 

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Test with gearcase drained. Too much pressure can fool you. Only needs a few
pounds, like three or so. Feel free to experiment with PSI.
 
Nice tester. Vacuum is actually a great way to test, however, if the leak is bad enough, a pressure test often finds it for you. I modified a radiator, coolant system tester. The threads are actually a 3/8 NC. I have suspect on shift rod o-ring too, that's usually the problem. I run 10 to 14 psi., have unit well drained and hold down the driveshaft, it may pop up. Use soapy water and move shift rod in order to exercise the o-ring. Once you see bubbles, you are certain thats it. You will either drive bushing out from the bottom with JUST THE RIGHT SIZE rod or punch....or you can cut some metric threads, just the right size....partway down into the bushing....then thread in a bolt, welded to a simple all thread....a nut, and a plate. The metric threads will not harm the bushing.
 

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It can be done.------My dad recalled going to a weekly radio program at the neighbor.----People there said -----" someday you will be able to see people talking on the radio "----All I need to say !
 
The only bad thing about a pressure test is, most seals are installed lip down to seal. When pressure is added it can press the lip against the shaft and pass the test. That why OEM manuals recomend doing both tests. Also all ya need is a pick, grease,2 beers and some patience to replace o-ring.... changed many ,many this way
 
Hey Pappy, great advice....but if I had to replace 3 O-rings in a row, Id never find my way back to the house, so thats why I made the tool. Wife says my limit is 5 Hamms. So I'm gonna try it next time....if you guys say it can be done....probably gotta be pretty warm out, eh? That is a pretty fat o-ring. My tool works pretty slick, in case I run out of Hamms.
 
Need to try Moosehead.....
cool.png
 
Probably too strong for me. I think Hamm's is only 4.7 percent ethanol. Sadly, I drink beer for the taste and refreshment....stupid, eh? I'm already too messed up to get buzzed!
 
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