Humminbird 998c SI - Manual (Page 24)

14 Transom Mount - DualBeam PLUS™
1. Locating the transducer mounting location
NOTE: If transom mounting is not possible because of a stepped hull or
cavitation noise, and you have a single layer fiberglass hull, In-hull installation is
an option. See Inside the Hull Transducer Installation for more information.
Turbulence: You must first determine the best location on the transom to
install the transducer. It is very important to locate the transducer in an area
that is relatively free of turbulent water. Consider the following to find the
best location with the least amount of turbulence:
• As the boat moves through the water, turbulence is generated by the
weight of the boat and the thrust of the propeller(s) - either clockwise
or counter-clockwise. This turbulent water is normally confined to areas
immediately aft of ribs, strakes or rows of rivets on the bottom of the
boat, and in the immediate area of the propeller(s). Clockwise
propellers create more turbulence on the port side. On outboard or
inboard/outboard boats, it is best to locate the transducer at least 15"
to the side of the propeller(s).
• The best way to locate turbulence-free water is to view the transom
while the boat is moving. This method is recommended if maximum
high-speed operation is a high priority. If this is not possible, select a
location on the transom where the hull forward of this location is
smooth, flat and free of protrusions or ribs.
• On boats with stepped hulls, it may be possible to mount the
transducer on the step. Do not mount the transducer on the transom
behind a step to avoid popping the transducer out of the water at
higher speeds; the transducer must remain in the water for the
control head to maintain the sonar signal.
Deadrise Angle
15”
Find a turbulence-free location at least 15" from the propeller(s)
and not in line with trailer bunks or rollers.
Level
Areas of Possible Turbulence
Rivets Strakes
Transom Hull
Stepped Hull
Step Rib