I wanted to know what RPM I'm running on my 15 hp yamaha for possible re-prop purposes so I got the Tiny Tach. I installed it, got it dialed in while in the driveway then went and launched. As soon as I twisted the throttle the screen went blank...nothing. I contacted the friendly folks at Tiny Tach and they gladly took it back and sent me a replacement. Again I installed it, got it dialed in, launched, twisted the throttle...screen went blank. Any suggestions? Am I correct in believing this thing is water proof? Are there other manufacturers of small tachometers?