I have been reading some of the post on here and 1 is right on about my needs, but still leaves me puzzled slightly. I have a 1994 mariner 75 hp that I have added 90 carbs to and have adjusted the timing accordingly. runs well. I have bought a ss competition tach so I can play with props and make sure I don't over rev. I understand it should be a 12 pole 6 cycle motor. which, by the directions say the tach should be set on 4. but at 4 I am showing idle speed of 1500 rpms and that doesn't seem correct. I have played with it and have settled on setting it at 8 but that seem incorrect based on the instructions. I was just checking to see if anyone has this tach and what they ended up setting it at. No response from the company. I like the way the tach looks but if it doesn't read right it may as well go swimming. thanks for any replies