Transmission problem?

Did a quick search but didn't find much. I have a '97 Malibu vlx with the walter v drive. I was out today and yesterday, everything worked good and normal but when we were going to head in I started to take off got up to about 10 mph and the boat seemed like it just kicked into neutral. No loud clunks or no bad sounds. Now it just acts like it won't go into gear and the drive shaft after the V drive won't turn when it is put into gear. Is there a sensor that I could check or something I could look into or does this sound like a blown tranny. All the linkage appears to work and the lever on the tranny looks like it moves with the throttle movement.