I am in need of a tach in a bad way that will work on a twin cyl 2 stroke outboard-one on the dash would be great but for now I just need to know how fast my motor is spinning for troubleshooting-anyone have suggestions for reading RPMs on the cheap,or maybe could send a private mssage if you have a tach collecting dust?my objective here is to see if my motor is spinning within factory specs wide open-