After rereading my post I think I was not clear enough. Ok. Ride out into chest deep water and as soon as the four wheelers exhaust goes under the engine will start skipping. You can hear it going "buh buh buh buh". ride back into shallower water where the exhaust comes out and power increases immediately because the four wheeler starts running smooth. However, sometimes you will be riding in deep water with the exhaust submerged and it will just go dead. If you step off the four wheeler and let the exhaust come above water it will restart. At this point the rest of the four wheeler is still under water. You may have to run it a minute or two to get it to blow the water out of the exhaust and get it to rev up right but it will start. Now, jump back on it and the exhaust goes under and it immediately loses power again. This four wheeler is full time 4x4 and has no mods running 27" tires. Oh, he told me that the crankcase is getting water in it but the air box is staying dry.
I am now wondering if the motor is just to weak to turn all 4 big tires and push the exhaust past the water. I am going to try putting stock wore out tires on it. Any other ideas are greatly appreciated.