What turns at crank speed? Calibrating Tach

[captainmurph]

I have new tach that needs to be calibrated. I also have a digital, portable tach that uses a tape marker that attaches to a rotating part that turns at crankshaft rpm.

Where's the best location on the engine to attach this tape to read crank speed?

Murph'

[BunnyPlanet169]

Do you have a small cover on the flywheel cover opposite the starter? You could remove that and stick tape on the flywheel. Or, remove the flywheel cover.

http://www.moyermarine.com/forums/album.php?albumid=150&pictureid=1710

[ndutton]

Accessory drive pulley turns at crank speed. It's what I used when performing the exact same calibration.

[Al Schober]

I use the shaft coupling (engine in gear). I have a DriveSaver which is somewhat reflective, so have to wrap the coupling with tape before putting on the reflective strip.