Modern fishfinders with side-scanning sonar technology provide incredible underwater detail, allowing anglers to see fish, structure, and bottom contours to the left and right of the boat. However, the performance of these systems depends heavily on where and how the transducer is mounted.

Proper placement ensures the sonar receives a clear signal without interference from turbulence or bubbles, which can otherwise distort the image.

When installing a transducer for a side-scanning fishfinder, there are two primary mounting options to consider.

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Option 1: Transom Mount (Most Common)

A transom-mounted transducer is attached to the exterior back of the boat, typically positioned slightly below the waterline. This is the most common installation method for recreational fishing boats.

Advantages

• Most affordable mounting option
• Simple installation with basic tools
• No drilling through the hull required
• Easy to adjust or replace if damaged
• Typically includes traditional sonar along with side-scan and down-scan imaging

Considerations

• Sonar performance can decrease at higher speeds
• Water turbulence from the hull or propeller may introduce bubbles that interfere with readings

Despite these limitations, transom mounts provide excellent performance for most recreational fishing situations and are widely used on small to mid-size boats.

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Option 2: Thru-Hull Mount (High Performance)

A thru-hull transducer is installed by drilling a hole through the bottom of the boat so the transducer sits directly in the water. Because it operates in clean, uninterrupted water flow, it can provide superior sonar performance.

Advantages

• Very clear sonar imaging
• Maintains bottom lock even at higher speeds
• Less interference from turbulence or prop wash

Considerations

• Higher installation cost
• Requires drilling through the hull
• Professional installation is often recommended
• Some deep-V hull boats may require paired transducers for optimal side-scan coverage

This mounting style is typically preferred for larger boats or installations where maximum sonar performance is required.

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Our Recommendation

For most recreational and fishing boats in the 17- to 22-foot range, a transom mount transducer is usually the best choice.

It provides:

• Excellent side-scan and down-scan performance
• Simple installation
• Lower cost
• No invasive hull modifications

This setup works well for the majority of anglers who want clear underwater imaging without complicated installation.

However, if your boat has:

• A stepped hull
• A deep-V hull with significant turbulence
• A larger inboard vessel

then a thru-hull installation may provide better sonar clarity and more stable readings.

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Why Transducer Placement Matters

Side-scanning sonar works by sending signals out to the left and right sides of the boat. If the transducer is mounted where water flow is disturbed by the hull, propeller, or trim tabs, the sonar signal can become distorted.

Proper placement ensures:

• Clear sonar images
• Accurate bottom tracking
• Better fish detection
• Reliable performance at different speeds

Even small adjustments in mounting location can make a significant difference in sonar quality.

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Need Help Choosing the Right Transducer Setup?

Boat hull designs vary widely, and the ideal installation often depends on:

• Boat make and model
• Hull shape
• Boat length
• Engine configuration

If you’re unsure which mounting style will work best for your vessel, it’s helpful to consult with a marine electronics specialist before installation.