Essential Outboard Boat Engine Gauges: What You Need To Know

Gauges are essential to monitoring the health and performance of your boat's engine. While some new boats have eliminated gauges in favour of idiot lights, engine gauges are your first line of defence against very expensive engine repairs. They can also help extend the life of your engine, improve your speed, and get better fuel economy. Modern gauges are almost entirely electrical, and a gauge consists of two parts: a sensor or sending unit at the engine, and a display or dial on your dashboard. There are several types of gauges that are necessary for outboard boats, including tachometers, water temperature gauges, oil pressure gauges, and voltmeters.

Tachometers

There are tachometers for all different types of boat engines, including outboard boat motor tachometers, inboard/outboard boat tachometers, diesel boat engine tachometers, and inboard boat engine tachometers. They come in both digital and analogue formats.

Some tachometers have additional features, such as a maintenance reminder, user shutdown, hour meter, and maximum RPM recall. When choosing a tachometer, it is important to consider the type of engine, the size of the boat, and the specific needs of the boat owner.

Water pressure gauges

Some popular water pressure gauge kits for outboard boats include the Sierra Lido Pro 2" Water Pressure Kit, the Sierra Amega 2" Water Pressure Kit, and the Sierra Lido 2" Water Pressure Gauge.

Voltmeter and ammeter

A voltmeter can be used to measure the voltage at the battery terminals, known as the "open circuit voltage". It is important to ensure that all accessories are switched off and that the battery has had 24 hours without any draw on it or charge put into it before conducting this test. A fully charged 12-volt battery will show an open circuit voltage of about 12.6 volts, while the same battery is considered fully discharged when the voltage drops to 10.5 volts.

Ampmeters also monitor the charging system but they monitor both current draw from the battery as well as current fed to the battery by the charging system. Therefore, if the alternator is not keeping up with the current being drawn from the battery, the system is considered to be discharging.

You can install a voltmeter at or near your main switch panel, connecting the positive (red) and negative (black) leads of the meter to the primary power input in your switch panel. If you have multiple batteries, you can wire the meter to the power input, and it will show the voltage of whichever battery is currently being input into the panel.

Alternatively, you can wire the voltmeter to another circuit inside the panel that does not directly consume power. This way, the meter will only be on when the battery switch is turned on. For the most accurate reading when the battery switch is on, ensure that no other lights or appliances are turned on, as this will cause a natural drop in voltage.

While a voltmeter is not the best gauge of your boat battery's condition, it can provide useful information to savvy boaters. By paying attention to the voltmeter when you are underway, you can gain insight into the health of your battery and charging system. With the engine running at cruise speed, the voltmeter will show the charging voltage, which should be between about 13.2 and 13.4 volts for batteries in good shape near a full charge. If the meter reads higher, your batteries may be drawn down or dying. If the voltmeter reads more than 14.5 volts, there may be an issue with your charging system.

By regularly monitoring the voltage displayed at cruise speed with minimal appliances energised, you can establish a "target" range to ensure your batteries and charging system are functioning optimally.

Oil pressure gauges

There are two main types of oil pressure gauges: mechanical and electronic. Mechanical gauges are simple, robust, and reliable, using a Bourdon tube to directly measure the engine's oil pressure. On the other hand, electronic gauges offer more precise measurements and additional features like alarms but require electrical power. They use a pressure sensor to measure oil pressure and display the reading on an LCD screen.

When choosing an oil pressure gauge, it is important to consider factors such as display and alert features, type of resistance, indication range, price, brand, and ingress protection. The display should be highly visible, and features like an LED backlight or warning sensor indicator light can be beneficial. European resistance gauges measure oil pressure in Bars, while American resistance gauges use PSI. The ideal indication range for European resistance is 0-10 Bar, and for US resistance, it is 0-80 or 0-100 PSI. Reputable brands in this space include Sierra, VDO, Faria, SeaStar, and Hardin. Ensure your oil pressure gauge has at least an IP65 ingress protection rating to protect against dust and water jets.

To install a marine oil pressure gauge, you'll need a kit that includes the gauge, sensor and bracket, connecting wires, and nuts and washers. First, decide on the mount location, ensuring sufficient clearance for the installation diameter and visibility from the driving position. Attach the bracket to the panel, then attach the gauge to the bracket. Connect the gauge to the sender using the provided wires, ensuring a secure and insulated connection. Finally, connect the power cable from the gauge to the power source, with the red wire as positive and the black wire as negative (ground).

To test your oil pressure gauge, you can follow these steps:

• Install a known resistor (e.g., 47-ohm or 100-ohm) to the gauge's signal input and ground.
• Connect the resistor between the signal input and the ground.
• Supply power to the gauge.
• Observe the pointer on the gauge. For a 47-ohm resistor, the reading should be around 40 PSI, and for a 100-ohm resistor, it should be approximately 80 PSI.
• If the gauge pointer does not move as expected, check the wiring and sender hookup.

The standard oil pressure for a boat is typically in the range of 20-40 PSI, depending on the engine type. Low oil pressure can indicate issues such as low oil levels or a malfunctioning oil pump, while high oil pressure can be caused by thick oil or a faulty pressure regulator, leading to excess wear and tear on the engine.

Fuel gauges

There are a variety of fuel gauges available for outboard boats, including both analogue and digital gauges. Analogue gauges feature a needle that points to the fuel level, while digital gauges provide a numerical readout. Some fuel gauges also include an LED backlight, making them easier to read in low-light conditions. Fuel gauges for outboard boats are available in a range of sizes, from 2 inches to 3 inches, to fit different dashboard configurations.

When choosing a fuel gauge, it is important to consider the resistance range, as this will affect the accuracy of the gauge. Fuel gauges with a higher resistance range, such as 240-33ohm, are typically more accurate and suitable for a wider range of vehicles. It is also important to ensure that the fuel gauge is compatible with your specific make and model of outboard boat.

Some popular brands offering fuel gauges for outboard boats include Sierra, Faria, and Moeller. These brands offer fuel gauges in a variety of styles and price ranges, with some gauges featuring black or white finishes to match different boat aesthetics.

Frequently asked questions