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sea and load conditions. Be alert the tachometer operation may provide an early indication of
difficulty, before it becomes irreversible.
Speedometer
The speedometer indicates the boat speed in miles per hour. Some types work using a spinning
wheel to determine the boat speed. Their accuracy can vary from the actual over the bottom
speed due to many factors. Other boat speedometers calculate the speed by amount of pressure
the moving water forces into a “pitot” tube. And some other speedometers use a GPS sensor.
These gauges should only be used as indicators of approximate speed and not used as absolute
speed indicators. NOTE: All Yamaha engines up to and including F250 utilize a pitot tube. In the
event that erroneous speed readings appear, it is likely caused by debris clogging the pitot tube.
Consult with your dealer on methods to clean the tube and restore normal operation.
Temperature Gauge
This is designed to monitor the operating temperature of your engine’s cooling system. A sudden
rise from the normal should be investigated to determine if there is an obstruction in the cooling
system. For Yamaha engines, a temperature warning light is incorporated in the tachometer.
Water Pressure Gauge
This gauge measures pressure in the engine cooling system. If the pressure changes from the
norm it could indicate a complete or partial blockage in the system or a water pump problem. If
this does not return to normal, your dealer should check it to make sure the cooling system is
operating properly. Low water pressure may also be caused by engines mounted excessively
high. NOTE: Factory rigged boats are not equipped with water pressure gauges.
Fuel Gauge
This gauge indicates the amount of fuel in the fuel tank. It is always prudent to follow the “rule of
thirds”, one-third of the tank to get the destination, one-third to return, and one-third in reserve.
NOTE: It is important to “calibrate” your fuel gauge during your first initial boat trip. Record the
fuel reading prior to fill up and how many gallons to top off the tank at each fill-up. Make sure the
boat is floating the same position. By subtracting the amount to top off from total fuel capacity you
can calculate gallons remaining in the tank for 3/4, 1/2, and 1/4 gauge readings. For Yamaha
engines, the fuel gauge is a bar graph incorporated into the speedometer.
This gauge is a measure of relative fuel supply and is not a calibrated instrument!
Voltmeter
This meter displays the voltage for the battery and charging system. The voltmeter should read at
least 12.1 volts when the engines are off and 13.4 volts when the engines are running. For
Yamaha engines, a voltage reading can be observed with the speedometer.
Hour Meter
The hour meter keeps a record of operating time and is very useful for scheduling maintenance.
This is incorporated into the tachometer for Yamaha powered boats.
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