Gauges, gauges, gauges: Replace/rewire questions...

[Philster]

My fiance decided that her new engagement ring was so nice that she went ahead and ordered me some Livorsi gauges and connectors that I was drooling over. She conspired with her brother-in-law, and they got them from CP via a link on the web (hey, pretty smart on their part, I guess). Despite ordering the wrong size (GPS) speedo and tach, they finally got the complete set with all the right sizes, nice mega rims in purple to match my boat.

So, I have a '96 Wellcraft Scarab 26' with 502 Merc/Bravo 1.

The tach and one other gauge are out/damaged. I went behind the dash and now I am confused. I have a marine wiring color chart, but still confused.

I see numerous black wires screwed to what looks like what I would call terminal screws/posts. Gotta say this is just one mess of ground wires. Yes?

The tach immediately confused me: one non-black group of wires is attached to clip mounting points on the back. There are at least three of them.

The voltmeter got me guessing further. Does it have an actual sender? Doesn't appear so!

I mean, my understanding is:

> that each gauge is going to need to be grounded (which appears to be a crude approach: just get black to black together on terminal screws/posts?) ??

> Every gauge has a 'sender' wire (from sending unit).
------ Does this apply to the the tach and voltmeter?

> Every gauge needs power and lighting.

Basically, I am stuck and my goal is to be water ready come Memorial Day weekend. I am afraid to start disconnecting stuff.

I need help. Actually, with my sudden biz trips coming up, I'd pay someone at this point, but if that can't happen, I need to wire these up.

 

[QC]

Re: Gauges, gauges, gauges: Replace/rewire questions...

Voltmeter power is it's sending unit . . . Step back from the Keyboard and think about that one for a second, Tach sender comes from the coil (engine wiring harness, same with Oil and temp).

 

[QC]

Re: Gauges, gauges, gauges: Replace/rewire questions...

Take a look at Merc service manual #16, section 4. That should help a lot.

 

[Philster]

Re: Gauges, gauges, gauges: Replace/rewire questions...

The voltmeter made sense, but when you doubt yourself, nothing does!

I will try to post some pics. I actually have a pretty easy setup. Best I can tell, the wiring is marine standard (purple = power, etc).

How about the black/grounds and my thinking there? They are just bunched together on the screws/posts as a way of running a continuous ground?

The gauges are going to share power and lighting, right? Do I hop gauge to gauge or am I supposed to pigtail all the power and lighting?

 

[Silvertip]

Re: Gauges, gauges, gauges: Replace/rewire questions...

Instrument panel wiring is as simple as looking at the diagram in the sticky at the very top of this forum. Every gauge except the speedo needs +12 volts and ground when the key is on. Yes - the blacks are all ground and the terminal post is a ground bus. The fuel gauge needs a sender. Oil pressure needs a sender. Water temp needs a sender. Voltmeters do not. When you connect +12 volts and grounds you have it. All gauges need lights so those are powered by the NAV/ANCHOR switch. Some boats have them wired to the +12 volt line so they are on whenever the key is on (dumb in my view but what do I know). The speedometer is pitot driven either through the outdrive/outboard or via separate pitot on the back of the boat.

 

[QC]

Re: Gauges, gauges, gauges: Replace/rewire questions...

The voltmeter made sense, but when you doubt yourself, nothing does!

Ain't that the truth!!!

 

[Philster]

Re: Gauges, gauges, gauges: Replace/rewire questions...

Instrument panel wiring is as simple as looking at the diagram in the sticky at the very top of this forum. Every gauge except the speedo needs +12 volts and ground when the key is on. Yes - the blacks are all ground and the terminal post is a ground bus. The fuel gauge needs a sender. Oil pressure needs a sender. Water temp needs a sender. Voltmeters do not. When you connect +12 volts and grounds you have it. All gauges need lights so those are powered by the NAV/ANCHOR switch. Some boats have them wired to the +12 volt line so they are on whenever the key is on (dumb in my view but what do I know). The speedometer is pitot driven either through the outdrive/outboard or via separate pitot on the back of the boat.

Brain fail: I had the proper Merc manual all along! I never noticed the instrument/wiring sections. I downloaded them when I first got the boat, and focused on engine/drive sections.

I am actually swapping in a GPS speedo head. I have the right output from my GPS to feed the signal. So, I will feed it power (purple), ground it (black) and hook up the blue NMEA output wire from the GPS system. I will send it seperate lighting control because...

I do have lighting control via the NAV rocker switch.

My wiring is color coded per the manual.

I don't know why I out thought myself, but it does help tons to look behind the dash and see the wire colors in synch with the manual and hear the great folks at iboats chime in.

Each gauge will get: power, ground, lighting and -- aside from voltmeter -- they all get the signal wire (color coded per gauge). The GPS speedo will get pretty much the same treatment, and it even gets its own signal (blue wire) from my GPS system.

When the key is turned, all gauges will have power and what they need to do their job. Their lights will be off until I turn on the NAV power.

THANKS! Feel free to say, "Hey, you got it! Now it's gonna be easy!" if you think so!

.

 

[imraan47]

Re: Gauges, gauges, gauges: Replace/rewire questions...

i have yet to find out how to exactly hook the backlight of guages to the nav switch. can you post how you did it?

 

[seabob4]

Re: Gauges, gauges, gauges: Replace/rewire questions...

i have yet to find out how to exactly hook the backlight of guages to the nav switch. can you post how you did it?

Jumper the blue wire from your gauge back-lighting to the bottom terminal on your Nav Lgt switch. That way, the back-lighting only comes on when your running lights are on. You don't have to do anything with the grounds...

 

[NYBo]

Re: Gauges, gauges, gauges: Replace/rewire questions...

All gauges need lights so those are powered by the NAV/ANCHOR switch. Some boats have them wired to the +12 volt line so they are on whenever the key is on (dumb in my view but what do I know).

Mine are wired to the key and I was going to change them. But then I read somewhere (probably Boating Magazine) that wiring them to the key helps keep the gauges free of condensation- the heat from the bulbs keeps them dry. Any comment on that before I wire up my new gauges??

 

[imraan47]

Re: Gauges, gauges, gauges: Replace/rewire questions...

Jumper the blue wire from your gauge back-lighting to the bottom terminal on your Nav Lgt switch. That way, the back-lighting only comes on when your running lights are on. You don't have to do anything with the grounds...

oh cool...that simple. thanks for the info. i will hit that up tomorrow and see it it works for me. none of the lights were working when i got the boat last season so in the process to get all this going and the end will be tomorrow if everything works.

 

[seabob4]

Re: Gauges, gauges, gauges: Replace/rewire questions...

I've done this a couple times...and I DIDN'T stay in a Holiday Inn Express last night!