Installing A Tachometer: A Guide For Boat Owners

Installing a tachometer on a boat is a handy feature to have. It provides information such as whether the motor has stalled or started and whether the prop is right for the boat. The process involves wiring up the power and selecting the number of pulses or cycles the outboard has to get the correct reading. The number of pulses is determined by the number of poles on the charge coil, which can be found in the outboard's instructions. The tachometer's calibration can then be adjusted accordingly. It is important to ensure that there is enough space on the dash for the tachometer and to check for any wires or obstructions behind it before drilling any holes.

Selecting the correct tachometer

• Compatibility with Your Outboard: Ensure that the tachometer is compatible with your specific outboard motor. Check the number of pulses or cycles your outboard has and select a tachometer that can accurately measure them.
• Accuracy and Reliability: Opt for a tachometer that provides accurate and reliable readings. Look for models with good reviews and a reputation for precision.
• Ease of Installation: Choose a tachometer that is straightforward to install. Some models may require additional tools or modifications, so consider your level of expertise and the complexity of the installation process.
• Features and Functions: Decide on the features you need. Some tachometers offer basic readings, while others provide additional information such as engine temperature or fuel consumption. Select a model that suits your specific needs and preferences.
• Display and Visibility: Consider a tachometer with a clear and easy-to-read display. Opt for a size and design that complements your boat's dashboard and ensures visibility while operating the vessel.
• Durability and Water Resistance: Given the marine environment, choose a tachometer that is durable, water-resistant, and capable of withstanding varying weather conditions.
• Price and Budget: Finally, consider your budget. Tachometers vary in price, and you can find models ranging from affordable to high-end. Select one that aligns with your financial plan without compromising quality and performance.

Remember to carefully review the specifications and requirements of the tachometer to ensure it is suitable for your boat's specific needs. Accurate readings from a well-chosen and properly installed tachometer can greatly enhance your boating experience and contribute to the overall safety and efficiency of your vessel.

Wiring the power

• Prepare the Necessary Tools: Before you begin, gather all the required tools and materials, including a tachometer, a drill, a hole saw (ideally with a diameter of 3-3/8 inches or slightly larger), a backing bracket, nuts, and wires. You will also need ring terminals, bullet connectors, and marine-grade twin core wire in an appropriate gauge (e.g., at least 18 gauge).
• Select the Installation Location: Choose a suitable location on your boat's dashboard for the tachometer. Ensure there is enough space and that there are no wires or structural braces behind the chosen area that could interfere with the installation.
• Drill the Mounting Hole: Using the hole saw, carefully drill a hole in the dashboard at the marked location. Take your time and apply firm, even pressure to ensure a clean cut.
• Create a Cover Plate (if needed): If the hole drilling doesn't go as planned, you may need to create a new cover plate. Measure the required size accurately and cut a new plate from a suitable material.
• Connect the Wires: The tachometer will have several wires that need to be connected. The wires typically include a calibration potentiometer wire, a backlight wire, a send wire (signal wire from the outboard), a ground wire, and an ignition wire (power wire). You may also need to connect wires for any additional features, such as a light.
• Determine the Signal Wire Colour: Identify the colour of the signal wire from your outboard. This information is crucial for the correct installation of the tachometer.
• Determine the Number of Pulses: You need to know the number of pulses or cycles your outboard has to get an accurate tachometer reading. This information can usually be found in the outboard's instructions or by contacting the manufacturer.
• Connect the Wires: Connect the wires from the tachometer to the corresponding wires from the outboard. Use appropriate connectors, such as ring terminals or bullet connectors, to ensure secure connections.
• Power Source: You can choose to power the tachometer directly from the battery or switch if you prefer. Ensure the power source can provide enough current to operate the tachometer.
• Grounding: Connect the ground wire to a negative terminal block or a suitable grounding location on your boat's electrical system.
• Secure the Tachometer: Once all the wires are connected, secure the tachometer in place using the provided bracket and nuts.
• Test the Installation: Before turning on the power, double-check all connections and ensure the battery is disconnected. Then, reconnect the battery and turn on the ignition. The tachometer should power up and display the correct readings.
• Calibrate the Tachometer: To ensure accurate readings, calibrate the tachometer according to the manufacturer's instructions. This process may involve adjusting the number of poles or pulses and testing the tachometer at different engine speeds.

Remember to take your time, follow safety protocols, and refer to the tachometer's installation instructions if you need further clarification on any steps.

Choosing the number of pulses

The number of pulses or cycles your outboard has will determine the correct tachometer reading. Tachometers normally have a small dial on the back with a number of settings. The number of pulses is determined by the number of poles on the charge coil. As the flywheel rotates, the tachometer counts the number of poles on the charge coil. For example, if there are six poles, the tachometer will count six pulses per rotation.

The number of pulses can also be determined by the type of engine. A four-cylinder four-cycle engine will have a different number of pulses than a six-cylinder four-cycle engine. Therefore, it is important to select the correct setting on the tachometer's dial. If the incorrect setting is chosen, the tachometer reading will be inaccurate.

Additionally, the tachometer wire colours are important to consider. The signal wire, which transmits the pulses from the engine to the tachometer, should be identified. This wire is typically grey but can vary depending on the engine. It is also important to ensure that the tachometer is receiving power and ground connections.

Finally, it is worth noting that automotive tachometers are not compatible with outboard engines. Outboard engines require a tachometer with the appropriate number of pulses per revolution.

Drilling a hole in the dashboard

Firstly, you need to determine the appropriate location for the tachometer on your dashboard. It is important to choose a spot that is easily visible and accessible, ensuring that there is enough space behind the dashboard to accommodate the tachometer. Once you have identified the ideal location, use a centre punch to mark the exact centre of the hole. This will prevent the drill bit from wandering when you start drilling.

Next, you will need to gather the necessary tools and equipment. A hole saw is the recommended tool for this task, as it will allow you to create a precise and neat hole. Ensure that the size of the hole saw matches the diameter of your tachometer. In addition to the hole saw, you will also need a drill and a block of wood to secure the dashboard during drilling.

Before you start drilling, it is crucial to take safety precautions. Put on safety goggles and gloves to protect your eyes and hands from any debris or sharp edges. Once you are geared up, securely clamp the dashboard to the block of wood, ensuring that the marked centre point is easily accessible.

Now, you are ready to start drilling. Firmly hold the drill with both hands and position the hole saw directly over the marked centre point. Apply firm and even pressure during the drilling process, allowing the hole saw to do the work. Take your time and be patient, as rushing may result in an uneven or inaccurate hole.

Once you have successfully drilled the hole, it is important to deburr and smooth the edges to ensure a clean finish. Use a file or sandpaper to carefully remove any sharp edges or burrs. This step is important for both aesthetic and safety reasons, as it will prevent injuries and provide a neat appearance.

Finally, it is time to install the tachometer. Carefully feed the wires of the tachometer through the drilled hole and secure it in place according to the manufacturer's instructions. Ensure that all connections are secure and properly routed. Test the tachometer to ensure it is functioning correctly, and you have successfully installed your new boat tachometer!

Connecting the wires

Identify the Wires:

Before you begin, it's important to identify the different wires on both the tachometer and the engine. On the tachometer, you will typically find terminals labelled as BATT or 12V for power, GND for ground, and SND or S for the tach signal. The tachometer may also have an additional terminal labelled "L" for the internal light.

On the engine, you need to locate the tach signal wire, which is part of the cable running from the engine to the helm. This wire usually has a bullet connector at the end. The colour of this wire may vary, but it is often grey.

Connect the Power and Ground:

Connect the power wire from the tachometer to a 12V power source. This can be done by jumping it to the "+12V" terminal on another gauge or connecting it to the navigation light switch or the "A" terminal on the ignition switch. Ensure the power source is activated only when the key is turned on.

Connect the ground wire from the tachometer to a negative terminal, which is usually identified by a ground symbol or a "-" sign. This can be the negative terminal of the battery or a ground terminal block under the dash.

Connect the Tach Signal:

The tach signal wire from the tachometer should be connected to the tach signal wire coming from the engine. This wire carries the pulses generated by the engine, which the tachometer uses to calculate the RPM. Ensure that this connection is secure and free from any damage or breaks.

Set the Tachometer Dial:

Tachometers usually have a small dial or switch on the back that needs to be set correctly. This dial corresponds to the number of pulses or cycles your engine produces per revolution. For example, if your engine produces six pulses per revolution, set the dial to "6P" or the corresponding number of poles. This setting ensures the tachometer interprets the signals accurately.

Test the Installation:

Once the wires are connected, test the tachometer by turning on the ignition and starting the engine. The tachometer should display the RPM, which you can validate by using a handheld optical tachometer or a multimeter to measure the frequency of the pulses. If the tachometer reading is incorrect, you may need to adjust the dial or check for any issues with the wiring or the tachometer itself.

Remember to consult the tachometer's installation instructions and your engine's specifications to ensure a proper wire connection. If you encounter any issues or have specific model information, it is recommended to refer to a certified marine mechanic or a boat forum for further guidance.

Frequently asked questions