I didn't think about that bc I figured the rubber Washer in the cap would Seal the air flow.
You're saying the Cap WITH the rubber washer does NOT create an air Tight seal?
If so, I believe my issue is probably fixed; bc I literally just crawled out of the Bilge with a flashlight and...
●Oil drained.
●New Gear Oil Regulator/Reservoir Cap with rubber Washer is ON.
●New Outdrive Gear Oil hose/line is installed and NOT showing an air leak with soap water at the transom or lower unit.
●Outdrive exterior gaskets show no air leaks with soap water.
●Oil drain/Fill plug bolts show NO...