J70TLCEM 1989- I'm installing a Navman 3100 Fuel-Flow Computer and it needs to power up when the ignition key is switched on. 80 milliamps max. draw. I was going to connect it's 12 volt positive lead to the tach using a ring terminal. My buddy insisted that this was a very bad idea and that I should find another source. I don't know why this would be a problem but I decided to check here before I proceed. If not the tach, can someone suggest another switched power supply ? I also have an hour-meter, trim/tilt gauge, and a fuel-gauge.