I’m having trouble with my 2005 25HP Mercury outboard. Using the tiller control, the motor will not shift into reverse. The problem began immediately after having the motor serviced at an authorized Mercury service center where the cooling water impeller was replaced. For the first time after the service, I backed the boat into the water, shifted into reverse twice pulling off the trailer and then to forward. The next time I attempted to shift into reverse, it would not shift. Neutral is ok and forward is ok, but no reverse. My wife returned the boat to the service center where the mechanic observed the problem. Several adjustments were made including dropping the lower unit for inspection. I checked the motor when it returned home. Without cranking the motor, I shifted the motor multiple times from neutral – reverse – neutral – forward – reverse. Everything seemed fine. The next weekend I put the boat in the water again and used reverse to back off the trailer. Once I got away from the dock, just out of curiosity, I tried reverse and it would not shift, again. My wife returned the boat to the service center again for an extended stay where I incurred another $250 parts and labor bill. This time the mechanic felt he had solved the problem. This time I picked up the boat and at the shop, I checked the motor. Without cranking the motor, I shifted the motor multiple times from neutral – reverse – neutral – forward – reverse. Again, everything seemed fine. On the way home, I put the boat in the water again and used reverse to back off the trailer, shifting from neutral to reverse twice. I shifted to reverse to pull back to the bank and then tried reverse again and it would not shift, again. The only difference I see is that when I pull off the trailer, I have to gas the motor to pull off. It seems that after this is done and I shift back to forward, reverse is no longer possible. I have also noticed that when rotating the tiller handle, it seems to rotate further in the forward direction than I remember. Does anyone know what the problem is? This is getting old and expensive. Obviously the mechanic is also baffled. Any help on this issue, for me and my mechanic, would be greatly appreciated.