Humminbird 1158c Combo, Installation And Operation Manual

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5. If you have the correct angle set on the transducer, yet lose a bottom reading at high
speed, adjust the height and the running angle in small increments to give you the ideal
transducer position for your boat. First, adjust the height in small increments.
NOTE:
The deeper the transducer is in the water, the more likely that a rooster tail of spray will be
generated at high speeds, so make sure that the transducer is as high as it can be and still be
submerged in the water.
If you are still not getting good high speed readings, you may need to disassemble the
transducer mounting assembly and re-position the ratchets.
If you do change the transducer position, re-trace the position of the mounting bracket
before proceeding.
NOTE: It is often necessary to make several incremental transducer adjustments before optimum high
speed performance is achieved. Due to the wide variety of boat hulls, however, it is not always possible
to obtain high speed depth readings.
6. Once you have reached a consistently good sonar signal at the desired speeds, you are
ready to lock down the transducer settings. Force the pivot to the Up position to gain
access to the mounting screws, then re-align the mounting bracket against the transom
of the boat to match the traced silhouette. Check the bracket position with the level
again to make sure it is still level, then mark the third mounting hole using a pencil or
marker. Unscrew and remove the mounting screws and the transducer assembly and
set aside.
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. 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
Transom Mount - DualBeam ™ PLUS
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