Proper tach setting

[GM165]

My tach seems to be reading wrong. Checked the back of it and the switch is set to 4. Options are 1,2,3,& 4. I have a straight 6 165hp Mercruiser. What is the proper setting?

Thanks.

 

[NHGuy]

Put it on #3 which is half of 6. Don't ask me why but they do that.