AV8TOR, It was suggested to me to rig up a MAGlite and point it at the front of the prop/engine while using the tach. The light should be pointed at the sensor of the tach. I intend to use a 20x8 or 6 Master Airscrew wood Schimatar (spelling?) prop. so keeping it under 8000 rpm should not be a problem. Thanks for your response.