TOPIC: plug in merc control wiring for tachometer..help

Hi all,
I am swapping out a vintage early 70's 6000 rpm quicksilver tach for an early 80's 7000 rpm quicksilver tach and am confused as to how to wire it. It's a 74 Merc 1500 on a 74 Hydrostream Vector I have the pigtail from the control box with white brown black. The original tach had black to positive and the brown to negative and the white powered the instrument lights. I had the brown wire going the SWITCHBOX output not the stator. The old tach worked fine and is correct vintage but I spin this past 6000 hence the tach change.
The "newer" tach is set up different, there is a pos and neg and a sender terminal. Plus a 4th lug to power the lights. So I know the white goes the 4th lug for the lights. Now I'm left with the two wires, black and brown...black on ground and brown on sender is a no go, I tried the obvious.
I'm guessing its gonna be like the original with black on POS brown on NEG and sender is blank? This tach also has the selection switch on the back, the switch I assume should be 6C when running off the switchbox? or should I go to 6 pole and run brown off a stator terminal?
I don't have the original tach instructions even though it is new.
Thanks,
Randy

might have to move to the stator.

Thanks Dave I was thinking Imight have to swap it at the motor but that still leaves the question of which wire where at the tach itself.
Randy

Hi, Randy, the white wire is switched +12V so you should be able to power both your lights and the "Pos" tach terminal off that same wire.

Black is ground which ties in at the switch and electrically connects to the battery ground cable.

Brown is tach signal that, for a newer-style tach taking input from the alternator, should be connected to the "signal" terminal on the tach, and at the motor, moved from the switchbox to either of the yellow-wire terminals on the rectifier.

These motors have a 12-pole alternator, so maybe there's a "12P" position on the switch. If not, see what the "6 pole" position does, you'll know right away if it's off or not!

BTW if the Quicksilver 7000 rpm tach has any model numbers on it, you may be able to find a wiring diagram or instructions with an internet search.

Last thought, regardless of how the old tach was connected, if the newer one has a terminal with distinctive (+) or (Pos) marking, it needs to be connected to switched +12V in order to power-up the tach.

Here are a couple of wiring diagrams, showing connections for the old-style and new-style tachs, respectively:

www.maxrules.com/oldmercs/Wiring/1966ona/35.pdf

www.maxrules.com/oldmercs/Wiring/1966ona/50.jpg

HTH.........ed

Thanks,
So it sounds like I have it wired OK at the tach. I have the +12 jumper in place black is on ground and brown is on sender. I just need to check the switch position and at the motor side move the brown to a stator wire ....lets see what happens...more to follow...tomorrow!
Randy

It's raining so no progress BUT still hoping someone has the actual instructions or wire diagram for back of tack when using the plug in three wire black/brown/white from the control.
Wish I never threw my instructions out from an install I did on my original 1500/Hydrostream back in the late 70's!
Randy

OK!! got brown on the stator and tach switch is to 6 pole (no 12 pole position) but one wire connect is half stator so that would be 6 poles..makes sense I guess,
all works fine..thanks everyone.
Randy

Glad you got it sorted out Randy, and it's great to see you back on the forum sir. Share some pics of what you're working on with us when you get some time, okay!?