I have a 2004 Bennington 2275RL that has a leaking transducer. I am pretty sure it is a Techsonic model that is mounter at the rear of my Left tube. Anyone know the replacement transducer needed to replace it with
It would depend potentially on what the depth display is - generally speaking if possible look up the make and model of the display and see what the compatibility is. For example if it's a garmin product, they typically have compatibility charts online as to what garmin replacement transducers will work. Techsonic appears to be a Humminbird predecessor company so I'd start there.
You could always try to find a direct replacement on ebay but it will probably be used. If the units are that old I would highly consider just starting over with a new depth finder as there are cheap models out there and they are currently supported vs something 24 years old.