tachometer wiring?

[Richard O'Brien]

Hi guys! I'm trying to hook up a new tach tonight, and the directions say set the screw for 4, 8, 12, or 20 posts? and they are marked as such. The question is what are the posts? The actual wiring went more smoothly.

[Catigale]

Number of cylinders on the motor maybe???

[RobertKing]

I believe its the number of poles on the alternator, that information for your motor should be in the owners manual or probably on the net.

[Catigale]

I like Roberts answer more than my first one. You also have to accomodate the pulley ratio (engine to alternator) to get the tach to convert signals from the alternator to engine rpm correctly....

found this at Balmar

TachometersAll Balmar alternators provide a source of un-rectified AC volt-age directly from the stator output. This stator output providesthe pulse required to drive most electric tachometers. Most cur-rent Balmar alternators feature 12-pole stator outputs (meaning12 pulses of AC voltage during each alternator revolution).Extra-large case 98-Series and older 9-Series alternators fea-ture 14-pole stator outputs.Many standard and aftermarket electrical tachometers feature some level of adjustment to calibrate thetachometer to your alternators pole settings and pulley ratios. If your existing tachometer does not provideany adjustability, it may be necessary to replace the existing tachometer with an adjustable model.

[Night Sailor]

Yes, it's the number pulsed per revolution. When I had to replace my original Mercury tach, I got a newer model Merc tach and it had a plastic rotary dial on the back of the tach to choose between numbers. The correct one for my '97 Merc 50 was the number 10. That information came from my owner's manual. If you don't have a manual, call any shop that works on your motor and they should know.

[Richard O'Brien]

Thanks guys! The default is 12 so maybe that's it? Can't find anything in the manual yet, buy you've got me headed down the right path. I think?Yes, Night sailor, It has a little plastic screw also. Maybe i can count the poles like Robert's observation?

Upon edit: Yes that was all there was to it. I Looked under the flywheel. and counted the poles, or rather the pole covers. exactly 12

The only additional information is: Purple/power, grey/sender, black/ground. no other wires needed for tach.