motor help.... need some insight

I put a 1993 90hp Evinrude VRO on my boat. The VRO was taken off when new and has had premix it's entire life. It runs great at low, mid and high speeds. Not even a sputter!! The problem that I am having is that it stalls when you put it in gear. I'm talking just flat out stalls. I've searched the net for the same problem but all I can really come up with is everyone saying it is the carbs. I'm 99.9% sure it is not the carbs. If the carbs were sticky or fouled it would never run this good. I need a few suggestions on what the heck I'm looking for? Remember other than dropping into gear, it runs great. I should mention that it will go into gear with the muffs on ..... no problem..... It is only when it is in the water and there is a load on it.