What's the proper procedure for pressure testing a TRS drive?
I assume the lower unit has to be removed so the dip-stick reservoir is closed.
How many PSI? Full of fluid or dry? How long should it hold pressure- overnight?

Test drive removed from boat 7 lbs is good it should hold pruessue for more than a day. For testing 20 minutes is good unless you have a problem and you are trying to find leak. Sometimes I have to take them apart to find leak becasue its leaking inside like where water goes up inside exhaust tube. I use a blow up boiler plug and use ratch strap to hold it in. Then you check internal for leaks. Drives from salt water sometimes leak from pin holes in casting. Marine Tex will fix problem. Grind it up and slip it in there. Remember to check resivor hose from helmet to transom plate. If try and test it on the boat you will have make something to hold dip stick in and breather on resivor take closed. Full or dry doen't mater Good luck

Thanks-

Also mix up some soap and water in spray bottle helps find small leaks