I have a 91 evinrude 225 looper, the tach i bought has a seperate connection for johnson/evinrude hookup, but it also has a adjustable setting for 6 , 8, 10 or 12 "pole position. I can find Nothing in manuals about which position I should select. The tachs not working and store guy was guessing on poles. Anyone know which is correct and what are the poles? thanks