How to Change the Speedometer in a Boat
Changing your boat's speedometer will require a few extra minutes in the course of your winter layup or your spring rigging out, but the time spent in changing an inoperative speedometer is cheaper than the fines you can incur for exceeding a posted limit, even if that "limit" is an ambiguous "reasonable and proper speed."
Other People Are Reading
Instructions
-
-
1
Unscrew the screws -- you'll probably need a Phillips screwdriver for this -- around the edge of the speedometer that hold the gauge in place. Lift the speedometer out of the dash as far as possible; there will be a thin, black plastic tube and, possibly, wires holding it in place.
-
2
Look under your dashboard or console and trace any electrical wires running from the back of the speedometer to the common power bus. Unscrew the screw holding the wire (probably red) to the power bus and pull the wire loose. Trace the wire to the common ground (the ground wire will be white or green and the ground is probably a grounding bus that looks like the power bus) and remove it from the common ground.
-
-
3
Pull the black plastic tube -- called the "pitot tube," it uses water pressure at the stern to force air into the speedometer, driving the indicator -- gently, to remove it from the back of the speedometer. Usually, the pitot tube is pushed into place over a barbed connector, but it may also have a plastic wire tie holding it to the connector. Use wire nippers to clip the wire tie, if necessary.
-
4
Push the pitot tube onto the barbed connector of the new speedometer. Trace the pitot tube back from the dashboard to its other end, under the transom of the boat. Have a friend blow -- gently -- into the pitot tube while you watch the speedometer to make sure it moves. If the speedometer appears to work correctly, run the wires through the hole in the dashboard where you'll be installing the speedometer and set the speedometer beside the hole; the hole lets a bit of light into the area under the dash where you'll be working next.
-
5
Connect the red wire from the speedometer to the common power bus, using the same screw you unscrewed to remove the old wire. Wrap the wire around the screw in a clockwise manner, then tighten the screw. Repeat the process for the ground wire, fastening it to the same screw on the common ground from which you removed the old speedometer wire. Turn on the boat's ignition, but don't start the motor, and make sure the speedometer's lighting works.
-
6
Set the speedometer into the hole and, using the screws provided with the new speedometer, secure the new speedometer in place.
-
1
Tips & Warnings
Remember that your GPS receiver has a speed display that's more accurate than a speedometer driven by the air pressure in a pitot tube. If your speedometer fails at an inconvenient moment while you're boating -- they always do -- check your speed using your GPS.
Before replacing your speedometer, check the pitot tube to see if it's kinked, broken, clogged with debris or marine life, or otherwise obstructed.
Familiarize yourself with the buoyage that's used where you boat at the beginning of each boating season. Most inland waters use the IALA Buoyage system, but each state may have "special" buoys, used only on the water in that state.
