A tachometer is a device that measures the rotational speed of a shaft or disk, usually in revolutions per minute (rpm). Tachometers can be mechanical, electrical, optical, or electromagnetic.
Tachometer testing is important for maintaining accurate engine performance data. Therefore, it is important to test your tachometer regularly to ensure that it is reading accurately. Read here how to test a tachometer on a boat.
What to Know about a Tachometer
The most common type of tachometer is the engine tachometer. It is found on gasoline-powered boats and measures the rpm of the engine crankshaft.
Other types of tachometers include alternator tachometers, electric motor tachometers, and hydraulic pump tachometers.
While most modern engines have electronic sensors that send data to an onboard computer, some older engines may still use mechanical linkages to connect the tachometer to the engine.
Step to test the Tachometer on your Boat:
Step 1: Check the Engine Speed
The most accurate way to do this is with a handheld GPS unit. Still, you can also use the speedometer on your boat if it is calibrated correctly.
Then, note the reading on the tachometer and compare it to the reading on the GPS unit or speedometer.
If they are not within a few RPMs of each other, then the tachometer is inaccurate and should be adjusted or replaced.
Step 2: Run the Engine and Check
Next, you should run the engine at different speeds and check the readings on the tachometer against the GPS or speedometer.
Again, check if the readings are within a few RPMs of each other.
Step 3: Check the Tachometer at Idle
As the engine is at idle mode, check the tachometer and compare it to the reading on the GPS or speedometer. Check whether they are not within a few RPMs of each other.
Notes for Checking Different types of Engine:
Electronic Sensor
If your engine is equipped with an electronic sensor, you can use a multimeter to check the accuracy of the signal being sent to the tachometer. Consult your engine’s manual for specific instructions on how to do this.
Mechanical Linkage
If you have an older engine with a mechanical linkage, disconnect the linkage at the engine and hand-cranking the engine.
Note the reading on the tachometer and compare it to the actual RPM of the engine as measured with a handheld GPS unit or multimeter. If they are not within a few RPMs of each other, then the tachometer is not accurate.
Helpful Tips for an Accurate Result
- Keep in mind that tachometers are designed to measure the speed of a rotating object, so they will not be accurate if the engine is not running at a constant speed
- If you are having difficulty getting an accurate reading from your tachometer, try moving it to a different location on the boat. Vibrations from the engine can sometimes cause inaccurate readings
- Make sure that the batteries in your handheld GPS unit or multimeter are fresh before testing the tachometer. Weak batteries can give inaccurate readings
- If you are still having difficulty getting an accurate reading from your tachometer, consult a qualified marine mechanic or engine dealer for assistance
- Most modern engines have electronic sensors that send data to an onboard computer. However, some older engines may still use mechanical linkages to connect the tachometer to the engine
- It is important to test your tachometer regularly to ensure that it is reading accurately
Conclusion
Tachometer testing is an important part of maintaining accurate engine performance data. By following these tips, you can ensure that your tachometer is working properly and providing accurate readings.
If it is not, make sure to adjust or replace it when neccesary. In case of any confusion, do not hesitate to reach out to us.