and nothing responds.

Do the servos respond? You have three sub-systems to deal with. The transmitter, the receiver, and the speed control. First the transmitter. As it is of a fairly recent vintage, it might have a 27mhz or 75 mhz system. Does it have a status LED or battery level meter. If that shows good we can move onto the receiver.

Receivers are in more hostile envrionment and tend see more problems. Given fresh AAs, you might see some activity in the servos when you plug in. Check the channel number and make sure it is a match to the transmitter you have. Like many of us who used the old 75mhz channels, we had litterally too many transmitters laying around and grabbing the wrong one on the way to the pond was a common problem.

As for the ESC, hansvonpensch has it right. Mechanical speed controllers are not worth keeping. There are too many good low cost ESCs out there to consider. ProBoat is OK . I have one. Also check the Viper brand line of marine ESCs of which I currently own five. They too are resasonalby priced and waterproof. And they seem to offer decent low speed performance.

Battery elimination is nice but not well explained in many ESC manuals. If you want more info, we can help with that.

I would love to see you post a picture of this boat. What condition is the hull in? Was it fiberglassed? If the hull is in good shape, would you simply consider revamping all the electrical components? Reliability is as important as good looks!