How to Install a Tach on an Evinrude Boat Motor

by Chris Stevenson

Boats with tachometers allow the boat owner to govern and moderate the engine's rpm rate during wide-open throttle operation. Yellow and red lines on the tachometer indicate caution and danger thresholds, warning the boat owner of engine speeds exceeding the manufacture's specifications. Keeping the engine within and under maximum rpm ratings extends engine life and promotes better performance.

Trailer the boat to a convenient work location. Use a socket to disconnect the negative battery cable. Remove the key or lanyard from the ignition. Open the tachometer kit, and lay out the pieces. Refer to the instructions for the mounting hole's required diameter. Locate a place on your dashboard for a suitable mounting location. Use the appropriate diameter hole-saw bit to drill a hole through the structure.

Depress and turn the small selector switch on the back of the tachometer with a screwdriver; this sets the correct pole position for your engine. For instance, 9.9 hp to 15 hp, 4-stroke engines -- manufactured after 2001 -- are set for six poles. All two-cylinder engines having less than 70 hp require 10 poles. All other engines receive 12-pole settings. Look on the back of your ignition switch and locate the main ignition wire.

Use wire strippers to cut a length of wire leading from the main ignition switch wire to the "IGN" post on the back of the tachometer. Strip both ends of the wire. Crimp two wire-eyelets on both ends.

Connect one end to the ignition switch pole with a nut; tighten the nut with a small socket. Run the other end of the wire out of the tachometer hole from the inside. Connect it to the ignition pole on the tachometer with a nut. Tighten the nut with a socket.

Locate the ground-wire pole on the back of the ignition switch. Use wire strippers to cut a length of wire long enough to reach from the ignition switch to the tachometer, routed through the hole. Crimp two eyelets on each end.

Connect one eyelet to the negative ground on the ignition-switch ground pole; fasten the nut with a small socket. Run the other end of the wire out the hole. Connect it to the ground pole on the back of the tachometer. Fasten the eyelet with a socket.

Use a screwdriver to remove the screws on the electrical-control-box lid. Look for the pole marked "Sig," "Signal" or "Alt." Use wire strippers to cut a length of wire long enough to reach from the control box to the tachometer location. Follow the routing of the boat frame.

Strip both ends of the wire with wire strippers. The control box poles might have male or female spade connectors; if they do, crimp one appropriate connector to the wire and push it down over the pole. If it has a nut connector, crimp on an eyelet and fasten the nut with a socket.

Loosen the back slider-bracket on the back of the tachometer; slip it inside the mounting hole. Reach your hand underneath the dashboard, and spread the bracket so it catches the backside of the dashboard. Use a small socket to tighten the bracket nuts; position the orientation of the gauge for proper up and down alignment. Use tie straps to neatly bundle any excess hanging wires.

Items you will need

About the Author

Chris Stevenson has been writing since 1988. His automotive vocation has spanned more than 35 years and he authored the auto repair manual "Auto Repair Shams and Scams" in 1990. Stevenson holds a P.D.S Toyota certificate, ASE brake certification, Clean Air Act certification and a California smog license.

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