Humminbird HDR 650 - Manual (Page 27)

7. Drill the third mounting hole, using a 5/32” drill bit. Use a marine-grade
silicone sealant to fill all three drilled mounting holes, especially if the holes
penetrated the transom wall.
NOTE: On fiberglass hulls, it is best to use progressively larger drill bits to reduce
the chance of chipping or flaking the outer coating.
8. Re-position the transducer assembly against
the transom of the boat, then hand-install all
three screws. Make sure that the transducer
location and the pivot angle have not
changed, then fully tighten all three mounting
screws (see the illustration Fully Tighten All
Three Mounting Screws). Snap the pivot
back down. If you have performed the
preceding
procedures correctly, the
transducer should be level and at the right
height for optimal operation.
Fully Tighten All Three
Mounting Screws
23 Transom Mount Transducer Installation