Originally Posted by
Walkabout7781
The older Merc/Mariners did not appreciate having the starting battery charged at over 2 amps, or so I was told. Doing so will burn out some of the electronic stuff that runs the tachometer. Been there. Don't do that! ALWAYS disconnect the starting battery if you need to charge it. However, other than the tach not working, my XR-4 didn't seem to care. Once you get it setup, or know it is setup well, you don't really need the tach IMO. However, until the setup has been altered or confirmed, you do need the tach to work.