Re: Pressurizing the lower unit.
Just get a rubber tip airgun/blower, and with 3/5 lbs (NO MORE!), stick it in a drain or fill hole. Plug the other with the screw/gasket. Spray soapy water on the rear seals, and top seals. You will know real quick. Drain/fill get new gaskets, and rarely the problem. Working a L/U now..fishline took out the rear seal..