90hp merc 07 2st tacho

[ericcs]

For the last month, my tacho is reading around 800/1000 rpm more than it used to. Haven't touched it, so i'm curious to know which end is more likely to be problem, the tacho or the where it gets it's signal from? I don't want to buy a new tacho and find it's not the problem.

[Cobbo1]

Not experienced with boats but I'd imagine it would be the same as cars where the tacho counts the pulses from the distributor/ignition source, most aftermarket tachos (again unsure how this works in the marine world) will have a switch on the backside so you can set for 4 cyl, 6cyl or 8 cyl, ie more cylinders more ignition pulses