Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
Normally no sealant is required for the sensor other than an O-ring, because the sensor screws down into the top of the through-hull fitting which is sealed independently. Generally, the paddle wheel transducer is constructed this way so that it can easily be cleaned at the beginning of each season and removed for the winter. You should have a plug that looks just like the sensor sans the paddlewheel and wire. The plug is used to seal the through-hull while the transducer is out, and both should have rubber O-ring fittings.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.