Transom Mount Transuder Intallation Instructions

With a wide variety of boat hulls being manufactured today most fish finder installations represent a unique set of requirements and obstacles to overcome. While this may seem like a daunting task at first, this article will help guide you through this process to success.

Step One – Transducer Location

Determining proper transducer location is critical for optimum fish finder performance at both low and high boat speeds. Before drilling holes in your transom consider the following to choose the best location for a transducer on your particular hull.

1) Turbulent water is often created from ribs, strakes or rows of rivets on the bottom of the boat, and in the immediate area of the propeller(s). Because this turbulent water contains a greater amount of air bubbles such areas need to be avoided in choosing the best transducer location. As turbulence created from propellers try to keep transducer location 15” or more from the center line of the transom.
2) If high speed operation of your fish finder is a priority actually running your boat on the water at wide open throttle will help ensure you have chosen the right location based upon the information above. Remember air bubbles reflect sonar so you will be looking for areas free of bubbles. Be sure to bring a buddy along to drive the boat for this step.
3) Transom mount location of transducer bracket should also allow the transducer to point straight down, or up to 5 degrees ahead. Pointing the transducer slightly forward will help with proper fish finder operation at high speeds.
4) If the hull of your boat is stepped mounting a transducer above the step may be possible, but be sure that this location is actually in the water at high speeds, not just idle. If the transducer is not making contact with the water the fish finder will not be able to operate.
5) In some hull designs the propeller is forward of the transom. In this case a transom mount transducer is not recommended because of the turbulent water created by prop wash.

Step Two – Drilling Holes In Transom Or Mounting Board

Before you drill holes in your transom I highly recommend the purchase of a plastic transducer mounting board. By using a mounting board you can relocate a transducer bracket or install other brackets without drilling additional holes in your transom.

1. Determine if your fish finder came with a mounting template for the transducer bracket. Without a template you may need to assemble the transducer/bracket in order to determine where to drill the necessary holes.
2. Hold the template on the mounting board or transom of the boat in the location where the transducer will be installed. Align the template vertically; ensuring the lower edge of the transom meets with the bottom corner of the template.
3. Next us a pencil or punch to mark the mounting holes on to the mounting board or hull surface. Using the recommended drill bit, drill the necessary holes in to the mounting board but not all the way through, or into hull. When drilling in fiberglass hulls be sure to start with a small bit such as 1/8” in order to reduce any chipping of the outer gel coat.

Step Three – Mounting Transducer Bracket To Transom

Follow these steps only if a plastic transducer mounting bracket was not used as described above.

1. Apply silicone sealant around the mounting holes drilled into the transom per above.
2. Next align the transducer assembly with the drilled holes in the transom and press against transom.
3. Now insert mounting screws and tighten finger tight, do not fully tighten yet.

Step Four – Adjusting Position Of Transducer

Typical transducer brackets will allow both height and tilt adjustment. Follow steps below to optimize transducer positioning.

1. Adjust the pivot angle of the transducer so its bottom surface is parallel with the length or bottom of the boat.
2. Next slide the transducer down so the rear is about 1/4 inch (6mm) lower than the front. If you run your boat in a lot of shallow water you may want to keep the bottom of the transducer flush with the bottom of the boat. This will keep underwater obstacles from ripping of the transducer. However, fish finder performance at high speeds will suffer.
3. Now fully tighten the screws. It may be necessary to retighten screws after 24 hours.

Step Five – Routing Transducer Cable

Several options exist for routing the transducer cable to the area where the fish finder display will be installed. Two simple options that exist is to simply route the transducer cable over the transom or pass it through the drain hole directly above the splash pan of the transom. Another option is to drill a hole through the transom above the waterline, pass the cable through, and then fill the hole with a silicone sealant. Inside the boat there is usually a channel or conduit used for other wiring that the transducer cable can be routed along. It is very important that the transducer cable is not cut. Also avoid running the transducer cable directly along power wires or a VHF radio antenna cable.