DST800 flap

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Tom,

The housing of flapper valve equipped transducer housing feature a hinge located slightly lower down the throat of the transducer's seat. The upper portion of the plastic valve is connected to the aforementioned hinge. The plastic valve is pressured inward by a length of sprung steel. The pressure of the water then forces the valve further inward and slightly upward against the valve's seat. Were one to apply a suction cup or other sealing device over the outboard face of the transducer, then the transducer may be extracted from the housing to test the valve for freedom of movement and to verify the operation of the aforementioned spring.