Effective fishing in waters with variable bottom relief is impossible without a high-quality sonar, but even the most expensive device is useless if its sensor is installed incorrectly. Inflatable boat owners often face the problem of water turbulence that arises from an inflatable balloon and a hard keel, creating "dead zones" on the screen. transducer The balance between the purity of the signal and the protection of equipment from shocks.
The peculiarity of PVC boats with high pressure inflatable keel (HPD) or rigid removable keel is the complex hydrodynamics of the bottom. Unlike aluminum boats, you can't just drill a hole here, and mounting on a transom requires taking into account the operation of the outboard motor. Installation errors will lead to the fact that you will see only air bubbles instead of fish, or, worse, lose expensive equipment on the first exit to the glissse.
In this article, we will discuss proven installation methods that will allow you to get a clear picture of the bottom even at high speeds. You will learn how to bypass the hard keel so that it does not shield the signal, and what angle of inclination to choose for your model. Lowrance, Garmin or Humminbird.
Choosing the Best Place for Installation
The first step is to visually inspect the transom and the bottom of the keel, and the main goal is to find the point where the flow of water around the cylinders and the keel becomes laminar (even) before it reaches the working surface of the sensor, and if you place the device too close to the keel, the rigid design will create vortices that the sounder perceives as bottom or fish.
The ideal place is considered to be a zone strictly in the center of the transom, but with a downward shift so that the working part of the sensor protrudes below the keel line by at least 1-2 cm. However, on boats with powerful engines and high speeds this may not be enough. In such cases, it is recommended to move the mount to the side, retreating from the keel projection to avoid falling into the “shadow” created by a rigid structure when the boat rolls.
⚠️ Warning: Never place the sensor directly above an inflatable cylinder without a rigid spacer. The vibration of the running motor will be transmitted to the soft side, causing constant oscillations of the sensor and blurring of the picture on the screen.
When choosing a location, also consider the length of the cable. The wire should not create loops that can be hit by the foot of a fisherman or a fishing line when catching a trophy. The cable should go to the device on the shortest path, but with a small margin to cushion the jerks.
Methods of attaching the sensor to the transom
There are several basic ways to fix equipment on a PVC boat, and the choice depends on the type of transom you have and how often you use the motor. The most common option is to use a regular plastic bracket complete with a sonar. It is attached to the squirrel board with screws or powerful screws with a wide hat, often through special plastic washers to avoid damaging the wood or plastic of the transom.
For boats with soft transmessants or temporary installations, adhesives are a great way to do this, and they use a special moisture-resistant adhesive or a two-component epoxy resin that is compatible with PVC fabric, and it's important to degrease the surface with alcohol or a special cleaner before applying the adhesive, and it's good because it doesn't require drilling, but it takes time to polymerize the composition.
- 🔹 Mechanical installation: drilling of the transom board, using bolts with nuts and counternuts for reliability.
- 🔹 The adhesive method: use of specialized adhesives for PVC, creation of a non-separable connection.
- 🔹 Strubs and brackets: temporary attachment to a removable transom board without damaging the boat itself.
If you choose the mechanical method, be sure to use a sealant to treat the holes. Even a microscopic crack around the fastener can eventually lead to depressurization of the transom bag and water entering the inflatable tubes.
Accounting for the effects of inflatable and rigid keel
The keel is the main enemy of the clean signal when mounted improperly. A rigid removable keel inserted into the slots creates a rigid wave that propagates backwards. A sensor installed in the zone of influence of this wave will go blind at speed. The solution lies in the height of the installation: the lower the sensor is relative to the lower point of the keel, the better.
However, lowering the sensor too low is also dangerous - there is a high risk of catching bottom vegetation, snags or stones, which will lead to the loss of the device. The optimal solution for boats with a pronounced keel is to use an elongated bracket or an H-shaped rack, which allows you to bring the sensor back and down, in the area of calm water, already flowing around the keel.
| Parameter of installation | Recommended value | Effect on signal |
|---|---|---|
| Height below the keel | 10-30 mm | Reduces cavitation. |
| Inclination angle | Perpendicular to the bottom | Maximum echo |
| Distance from cylinder | Minimum 5 cm | Reduces vibration. |
Owners of inflatable keel boats (HPD) should remember that when pumped to operating pressure, the keel hardens and also creates a wave, in which case it is important not to press the sensor with the weight of the engine, if the mount is combined, so as not to deform the scanning area.
Adjustment of the angle of inclination and depth of immersion
The correct angle of inclination of the working surface of the sensor is critical for operation at different speeds. When the boat moves, the nose rises, and the transom, accordingly, goes down. If the sensor is installed perpendicular to the water in the parking lot, then on the move it will pick up the nose, losing contact with the bottom. So the static angle of inclination should compensate for the diffusivity of the boat in the planing.
The standard recommendation for most models is to set the sensor so that the back of the sensor is lowered 1-3 degrees below the front, which ensures stable contact with water mass even at sharp accelerations. The angle adjustment can often be done by placing washers under the mount or using the rotary mechanism of the standard bracket.
The depth of immersion also requires fine tuning, and the sensor must be submerged in water so that its upper edge is at least 5 mm below the waterline, but does not create much resistance. Critically important Check the sounder at different speeds: if the picture breaks at full gas, then the sensor is too high and captures air.
⚠️ Warning: When setting the angle of inclination, avoid situations where the sensor is looking vertically down in the parking lot, and on the move this is guaranteed to lead to cavitation and loss of signal.
Cable protection and electrical safety
The sensor cable is the most vulnerable part of the system, and on a PVC boat, it's subject to constant bends, ultraviolet light, and mechanical stress, and when you put the wire along the side or across the transom, you need to use a corrugated tube or a special cambring, which will protect the insulation from rubbing against the rough surface of the cylinders.
Pay special attention to the location of the cable's entry into the sensor body, which is the point of maximum stress when jerking, and it is recommended to lock the cable at a distance of 10-15 cm from the head of the sensor using plastic clamps or insulation, creating a small hinge-shock, which will take the first hit on the hook.
- ⚡ Insulation of compounds: All twists and rations should be carefully insulated with a thermal shrinkage with a glue layer.
- ⚡ Routing: Avoid laying cables near fuel hoses or sharp corners of the transom board.
- ⚡ Fixing: Use plastic clips or Velcro straps without clamping the cable so as not to disturb the integrity of the veins.
To connect to the battery, use a fuse mounted in the break of the plus wire as close as possible to the power source, which will save the expensive electronics of the sonar in the event of a short circuit, which can occur when vibration or water enters the connectors.
Testing and elimination of interference
Once installed, you need to test the system on water, anchor at a depth of 3-5 meters and assess the clarity of the bottom line. It should be smooth and continuous. If the line is interrupted or "cruising", check the angle of inclination and the absence of air bubbles on the working surface of the sensor.
Then get on plane, and if you lose the image at speed or you get vertical interference bands, you're going to get air (cavitation), and you're going to lower the sensor down or change the angle, and you're going to have to get interference from the outboard motor itself if you're too close to the lower unit.
A common problem is interference from other electronic devices, and if you have a GPS navigator, a radio station, or a second sonar, their frequencies may conflict. Garmin or Lowrance Try changing the operating mode of the sonar emitter or scanning frequency.
Check your attachment status regularly throughout the season. Vibration can unwind even tight nuts. Seasonal prevention will take no more than 10 minutes, but will save you from losing equipment while fishing.
FAQ: Frequently asked questions
Can I glue the sounder sensor to a double-sided scotch?
Use of conventional double-sided tape is strongly discouraged. In water, temperature and vibration conditions, it will quickly lose its properties. For gluing without drilling, use only specialized PVC sealants or epoxy compounds intended for underwater use.
Why does the sonar show arcs but not see fish?
This can be due to the wrong sensitivity (too high or low) or the wrong angle of the sensor, and the "arcs" can be artifacts from a working motor or a neighbor's sonar, try to reduce sensitivity and check the angle of inclination of the sensor.
Do I need to take off the sensor for the winter?
Yes, it's recommended that you take the sensor and the head unit down for winter storage, that the plastic becomes brittle in the cold, that the water inside can freeze and damage the case, and that you keep the equipment in a warm, dry place.
How does the color of the PVC boat affect the sonar?
The color of the boat does not affect the sound sound sounder, because it uses sound waves rather than light, but dark boats are more heated in the sun, which may indirectly affect the temperature of the water in the near-surface layer, but this does not affect the quality of the scanning of the bottom.