When we no longer needed the factory transducer hole under the forward cabin, we simply used the spare black plastic blanking plug that Pochon kindly left there tied to a little string.
Hull No. 350 came from the factory will all Raymarine and Furuno equipment, including:
(1) a speed transducer under the forward cabin
(2) a depth transducer under the space between the forward head and the forward hanging closet
When we updated the instruments, we installed an Airmar DST800 supplied by B&G as part of their wind/depth/speed package. Works under all conditions, including heavy rain. It measures depth, speed, and temperature.
Cheerio,
Peregrinus
At anchor, Venice