A DIY Tachometer for Small Motors

Small motors also sometimes benefit from the tachometer.

The tachometer is used to measure the use of the small engine. Engines need regular maintenance, especially after they have been used heavily. Tachometers are helpful for small engine owners who have many responsibilities and sometimes forget to perform regular maintenance on the engine, since owner can regularly check the tachometer to determine when to service the engine. Many larger engines come with a tachometer already installed, but the same is not true for smaller motors.

Things You'll Need

• Screw driver

Instructions

1. Locate a place on the motor where the tachometer is the least likely to be damaged. For example, on a boat motor, install the tachometer as far away from the propeller as possible.

2. Locate where you will place the mount for the tachometer. Drill holes into that location that corresponds with the mounting holes on the mount. Do not drill holes into the engine crankcase or a gas tank. Contact the manufacturer or dealer if you are not sure whether you can drill into a particular part of the small engine.

3. Put the wire over the channel on the mount and push it down using a flat-head screwdriver. Make sure that the wire is sitting completely in the channel. Attach the meter to the mounting surface, using screws that come with the tachometer.

4. Wrap the spark sensor cable around the spark plug cable. This causes the wire to detect the electrical signal. After wrapping the pick-up wire around the spark plug, tie a tie-wrap around the loose wire to secure it to something, so it does not move and cause the pick-up wire to unravel. If the pick-up wire cannot reach the spark plug wire, replace it with a wire that has the same outside diameter and doesn’t have less than 22 gauge. The wire should not be longer than 8 feet.

5. Attach the ground cable to the grounding point on the small motor.

6. Review the engine’s specifications and configure the tachometer based on these specifications. Factors that influence the tachometer include whether the meter is a two- or four-stroke engine and how many cylinders the engine has. Look up the maximum RPMs for the small engine and determine whether these RPMs will exceed the maximum RPMs for the tachometer.

Tips & Warnings

• Do not place the tachometer in a place where temperatures surpass 125 degrees. If you can touch the surface without feeling comfortable it is safe for the mount. Some mounts can survive hotter temperatures. Check the tachometer’s specifications.

References

• Majestic Trust: Small Engine Tachometer Basic Guide
• Jacks Small Engines: Wiring Instructions - Inductive Surface Mount Meters
• Small Engine Tachometer: Small Engine Tachometer Guide