Tachometer

[Ted]

Can anyone recommend the proper "rpm instrument" to calibrate the installed tachometer on the boat (diesel engine)? I saw a surveyor use a visual strobe light and a piece of reflective tape on an engine pulley to measure rpm, but haven't been able to find one of those for sale... just wondering, do the tachometers for sale in auto parts stores work? How do mechanics independently verify rpms on car/truck diesel engines? "Please and thank you"!

 

[John Tesoriero]

Tach check

You don't need a dedicated tachometer calibration tool. Put a small piece of white paper or tape on your main engine crankshaft pully. Shine a standard flourescent lamp on the engine (in semi-darkness). At 1,800 RPM you should see four stable white marks hovering at about 90 degrees from each other. At 3,600 RPM there will be only two marks, 180 degrees from each other.

 

[John Tesoriero]

Tach check

You don't need a dedicated tachometer calibration tool. Put a small piece of white paper or tape on your main engine crankshaft pully. Shine a standard flourescent lamp on the engine (in semi-darkness). At 1,800 RPM you should see four stable white marks hovering at about 90 degrees from each other. At 3,600 RPM there will be only two marks, 180 degrees from each other.

 

[John V.]

Well...

That flourescent light trick doesn't work well at a mooring!