Just hooked up tach to a 1975 65HP Merc. on a 16 bow rider (1975 Tempest). I put signal setting to 6 pulses. I am registering about 1000 RPM's when I am idleing. But WOT I am off the scale (7000 RPM) which only goes up to 6000 RPM's.Right now I am registering about 28 mph.<br /><br />Can this be registering right? Should I change to 4 pulses? I think I have 17 pitch prop.