Got a used Gaffrig monster Tach that I installed. The back of the gauge has red/ ign, blk/grd, grn/sender, wht/ light, then 2 looped wires. The sticker says for a 6 cy snip the brown wire. I have it hooked up to a 2.5 outboard. The RPMs are way wrong!! The old gauge worked with the engine and wireing... So, is there something I did worng with this monster tach wireing or is the tach just junk???? Its acting like its set for a four stroke, but I see no way to change anything no prob settings

Thanks for any help,
Dan