Raymarine - P79 Adjustable In-Hull Transducer - E66008. The P79 adjustable, in-hull depth transducer is ideal for boats with fiberglass hulls looking for a fast and easy installation, high-speed performance, or those who want to minimize drag. The transducer installs inside of the boat's hull, transmitting and receiving echoes through the solid fiberglass bottom with no hull protrusion whatsoever.. P79 comes with an innovative flange that installs on the inside of the boat's hull using quick-set