Setting rpm on 3.0 mercruiser

[Pdevito]

I can't find the old school tachometer. So I have this one says you wrap at 5 times around a spark plug wire. So my question is which wire? Or can I use the stub Out grey wire? That's the one that's used in the falctory. They're saying set it to 750 on the muffs in my yard and then when I get it in the water put it in gear and get it to 650. Any ideas

 

[airshot]

All marine engine mfgrs state to adjust idle speed and idle mixture adjustment if applicable while underway, in the water, not on muffs or in a barrel. Your call whether to follow instructions or do your own method..

 

[Pdevito]

I will do final in the water . Just dont want wife to have trouble keeping it running whrn i drop it in