Stalling Problem

I am rebuilding a 1989 Renken Classic 2000 and have a slight problem with the engine/outboard? It is an I/O, chevrolet 350 260hp block with an OMC outboard I believe. Here is the problem: When the boat is first launched and I start the engine, as soon as I shift into reverse to back away from the boat ramp, the engine will stall out. I have no idea what to do about this. Even after the engine is warmed up, it will still stall sometimes after being shifted from drive into neutral or reverse. Not as much as when it is cold, but it still happens sometimes. someone please help me!!!!!!!!!!!!

 

Hello
I am more familar with merc stern drives and on mercs there is a switch on the shift linkage that kills the power for a split second to the ignition when shifting into gear, if the linkage is a little out of adjustment it will kill the engine.
Tom