Came across the interesting setup below.
OpenPilot is a next-generation Open Source UAV autopilot, it is a highly capable platform for multi-rotor craft, helicopters as well as fixed wing aircraft. It has been designed from the ground up by a community of passionate developers from around the globe, its core design principals are of qualit…
At quick glance this seems to have more then what might be necessary for model boats. But I think it would be an interesting exploration to try and mod it to fit. Give the old model boat a little AI .