My tachometer jumps at various rpms at all speeds on my 1999 evinrude ficht motor. Is this due to a defective tach or is something else in the engine causing this problem.
I would look for loose connections,
start behind the tach, remove and reinstall wiring or plug.
Check connections at the rectifier,
spray elec cleaner on the main harness plug contacts too.
Check battery connections, no wing nuts.
