Any thoughts on some kind of water scoop to install on outdrive to force water in? Shouldn’t be necessary, but I am leaning towards a flow issue also.

Could be a problem with the water tube in the lower unit or a restriction in the lower unit which supplies the water.

All water intake hoses, gaskets and o-rings have been replaced.

Clear hoses in place for intake air leak and head gasket leak bubbles test.

PROBLEM DIAGNOSED!!!
Head gasket leak. I was fooled by a cold engine compression and leak down tests that looked perfect. Clear vinyl hose test should have been my first test, but since leak down is supposed to be confirmatory I jumped straight to that. Good grief. It’s what I least wanted it to be. Now to figure out which head by attempting leak down on warm motor.

Pressure hose from raw pump on left, water out from block and heads on right.

Well, doesn't really matter which head, you're going to replace both gaskets, right??

Exactly, if one is bad the other is not far behind.

Yeah I decided the same thing and ordered both sides. This engine was rebuilt less than 100 hours ago, but about 8 years. Guess I should get out more.

Ran compression and leak down with engine warm. Not sure I would have landed on head gaskets without the bubble test.

Wow - what a saga. Glad you found it Bro!