I have a 20 pole force tach that I replaced for my 175 v6 johnson tach, I think the dealer made a mistake. It has "20 pole force" imprinted on the back and I only max out at 2200 rpm on this tach. When I asked the dealer if it was the correct one, he said I have to calibrate it. I am learning that I need a 12 pole, can anyone tell me what the difference is and what the poles mean?
