Mercury 175 hp EFI stalling out after revving and then dropping back to idle; no load
I am working on a 2000 Mercury 175 hp EFI OT154068. The customer put his battery cables on in reverse. I had to replace 3 cdms, the cdm wiring harness, electrical module, and repair the black/yellow wire on his the main harness. The engine is running good in the water under load. The engine is idling fine in gear and out of gear.
The only issue that I notice is that if you rev the motor up (out of gear) and then drop the throttle back to neutral quickly, the engine stalls out. It does not stall out if you do the same thing while in gear.
Any ideas what could cause this while out of gear only? Thanks for your help.