Engine Stalls when throttling in reverse
 

I have a 1994 Regal with a 4.3 L Merc (Alpha 1 Gen II).

I have recently restored this boat from the hull up. It runs well, but has one big issue.

I have full function in Forward (runs like a bat of h***). When i shift into reverse it shifts well and runs fine in reverse at idle speed. As soon as I try to give it a little gas, it stalls (a real pain at the docks). I would have initially thought it was the shift cables or shift interrupter switch, but it does actually shift (and turn the prop) in reverse w/o issue and forward works very well. When in neutral, i can rev the engine just fine in the reverse direction.

I am stumped. Thoughts?