How to check gages!

[Piedog]

Can someone tell me how to check the volt, tach and fuel gage to see if they are working or if there is a problem with them!

 

[Mark_VTfisherman]

Re: How to check gages!

Ummm. So I guess it is safe to say they are not registering anything now? Typically, one would just start the motor. Maybe you can repost with some details and someone will probably be able to help you out.

 

[seabob4]

Re: How to check gages!

PD,
So, we start, once again, with the multimeter. You'll have a purple wire (most likely) going to one post on your tach, then daisy-chaining to your trim and your voltmeter. With the ignition in the "run" position, check for voltage on the purple wire. That is "ignition power" coming from the motor, not from your boats house side. If you have 12V+ on the purple wire, than your voltmeter should read about the same, your trim gauge should change as you tilt the motor up and down. The tach? You have to run the motor for that one.

If, with the key in the run position, you have no voltage, put your meter on continuity, and check the grounds on the back side of your gauges with your ground buss bar under the helm. The motor and the boat systems share the same ground. If you have a good ground, and good voltage on the purple wire, then your gauges are shot. If you don't have a good ground, then you have a break in the ground wire somewhere in the engine harness.

Try this approach and get back with your findings...

 

[Silvertip]

Re: How to check gages!

Actually the motor and ground bus at the helm do not always (and generally don't) share the same ground path. The boat harness (the small pair of wires) that run from the battery to the fuse panel feed the fuse panel and its ground bus. The engine gets its ground through the large battery cable. The cable that goes up front to the console from the engine also contains a ground, but it is intended to power only the gauges and would not likely be terminated at the fuse panel since this may or may not cause a "ground loop" and present issues with sensitive electronics. Picking nits here but just want you to know that ground may not "always" be what you think it is.

Since you apparently have multiple gauges that are not working, it is likely +12V or ground feeds to those gauges are loose or disconnected. The only gauge that is electrically engine dependent is the tach. All others are "boat" related.

 

[seabob4]

Re: How to check gages!

...Actually the motor and ground bus at the helm do not always (and generally don't) share the same ground path.

Excuse me, but I've been building boats for 15 years at the OEM level, Wellcraft, Aquasport, Hydrasports, Intrepid, Stamas, and Proline...and ALL the grounds were tied into the same buss, or busses linked together. Battery grounds were tied together, as well as 120AC grounds to the 12V-, and bonding wires...

Where you get what you said, I have no clue...

BTW, the voltmeter and trim gauge are "engine" related, not boat...

 

[Silvertip]

Re: How to check gages!

I guess we will have to disagree since we (at least I) have no idea at this point what boat this poster has. On the recreational boats I deal with that is not "always" true as I posted. If what you imply is "always" true, then why would there be the need to run 8 or 10 gauge +12 and ground wires from the starting battery to the console when there is +12 volts and ground available in the engine harness. The answer is really quite simple. The engine harness on an OUTBOARD is not intended to serve the power requirements for the entire boat. A real test of your theory would be to pull the negative battery cable at the battery or the engine and then hit the key. If the engine harness and/or ground wire in the boat harness went up in smoke you know the ground in the engine harness is bonded at the fuse panel or somewhere else in the "boat harness". Neat system right? If nothing happened, you know it isn't which is exactly the case on both of my personal boats. The wiring on larger boats with shore power setups, generators, and other complex wiring schemes makes it necessary to pay more attention to bonding. I would also agree with you that boats with SmartCraft and similar data systems may have bonded panels since data requires noise-free circuits. A conventional Merc outboard harness has a 16 gauge ground pigtail off the ignition switch magneto ground side and is the only ground in the harness. That wire can be used in a number of ways. 1) ground for the instruments. 2) bond to the ground bus which requires gauges to be grounded to the bus. 3) Not used at all since the ground side of the magneto kill circuit is already at engine ground which is at battery ground through the battery ground cable as is the fuse panel ground through the "boat harness ground wire" (which is bigger by the way). So you see we really agree -- just not "always".

 

[seabob4]

Re: How to check gages!

These are pics of a boat I just re-wired...completely.

Pic 1, you'll notice only 3 leads off the ground terminal on the battery, engine ground, battery charger ground lead, and "house ground" going to here...

From the bilge ground buss, you will see the appliances living in the bilge to be grounded here. The only lead running forward to the helm is the 6GA yellow, which ends up here...

The helm ground buss is the terminus for the all the helm appliances. Never is the engine harness ground touched, as it shouldn't be! The engine ground and the house ground are mated at the battery, and the DC ground dissapation for electrolysis and stray current are achieved through the engine zinc...

BTW, yellow is the choice for CE 12V-. Soon, you won't see any more black wire on boats...

 

[Jeepster04]

Re: How to check gages!

These are pics of a boat I just re-wired...completely.

http://s259.photobucket.com/albums/hh301/seabob4/183 Flats/183 Flats Album 2/DSCF0759.jpg

Can you tell me where you got those bus bars? Ive been looking for something similar and Ive not been able to find anything that big.

 

[seabob4]

Re: How to check gages!

Jeepster,
Do you like the ones under the helm? Copper, 10 #10 positions, 1/4" studs on the ends. $20 for a pair, shipped, brand new. PM me if you're interested.

 

[Piedog]

Re: How to check gages!

Sorry guys, I have a 1985 Challenger Pro Sport Fisher. I started pulling wires out today! Seems like there was a good 10 miles of unused wiring in the boat. With that said, now I have it down to the basic wiring. I traced out and replaced both the front and back tilt/trim switches, at first the back one would not work found it to be a ground wire problem. Also the boat came out new with a 12/24 volt run/charge trolling system. I changed out the 12/24 volt trolling motor plug located on the plate at the stern with a new 12 volt trolling motor plug removed the 12/24 volt switch and drilled out the hole and put a new power outlet in its place for use with a spot or blacklight. Now since the where 2 sets of battery wires coming from the back of the boat to the trolling motor I decided to leave the other set of wires for furture use. I then installed new Nav stern light holder and bought new Nav stern light for it. So along with a couple of accent lights on each side of the front deck wiring is all done up front.
Now to the back after getting rid of all splice and unsed wires I replaced one of the water inlets that was broken and check to make sure the other were good and tight. installed new bilge pump secured it into place and check the airator pump to see if it worked. it was good.cleaned up my battery cable connectors seems like each on of them at 2 or 3 wires running in with them. Now I have 2 batteries with my motor wires only running to the cranking battery and 2 wires only running to my deep cycle battery from my trolling motor.

Thanks to all of you on here with some great advise.

 

[Piedog]

Re: How to check gages!

Question, should I bond the negatives on each battery to each other ?

Question, there is a plug that comes out of the front of my controls , it has 5 wires in it 3 of the wires go to my tachometer the other to are wire tied back one wire is whilte and the other gray. does anyone know what they are for. 75 Mercury motor. also should my +12 that comes through the controls only go to my tach, or should it go to the tach, volt meter and fuel gage.


Thanks for the help!

 

[surrender]

Re: How to check gages!

You should have 12 volts at the three gauges. Some are wired to get power when the key is in the run position some not. The grey wire is usually the tach sender wire from the engine. It is with OMC.

 

[seabob4]

Re: How to check gages!

Question, should I bond the negatives on each battery to each other ?

Yes.

 

[seabob4]

Re: How to check gages!

Question, there is a plug that comes out of the front of my controls , it has 5 wires in it 3 of the wires go to my tachometer the other to are wire tied back one wire is whilte and the other gray. does anyone know what they are for. 75 Mercury motor. also should my +12 that comes through the controls only go to my tach, or should it go to the tach, volt meter and fuel gage.

Mercury tach sender wire is gray, this might explain your tach not working. The purple wire is "ignition power", only has 12V+ when the key is in the run position. Daisy chain the purple to your voltmeter, then to your fuel gauge. The third is ground, coming from your motor. Daisy chain that as well, from tach to volt to fuel.

 

[seabob4]

Re: How to check gages!

It would seem my post was edited by someone other than myself. If a mod has a problem with one of my posts, please PM me...

That would be the courteous thing to do...

Bob C

Update: Sorry Bob_VT, didn't see your edit. Resizing now...(give me a few...)

 

[Piedog]

Re: How to check gages!

Mercury tach sender wire is gray, this might explain your tach not working. The purple wire is "ignition power", only has 12V+ when the key is in the run position. Daisy chain the purple to your voltmeter, then to your fuel gauge. The third is ground, coming from your motor. Daisy chain that as well, from tach to volt to fuel.

Ok I checked while I was working on the boat today all 3 wires that you speak of are connected , I also know that I have power and good grounds on each of the insturments because when I turn on the key they light up but none of them actually work the volt meter arm never moves, the fuel gage still reads empty and the tach doesnt work when the motor is running either, also can someone tell me what the 2 extra wires are for that are in the wiring harness that comes out of the front of the motor controls. 1 is brown with white stripe and has a round connector end on it and the other one looks to be while with a black stripe on it and has a female end on it like you would plug into either a male connector or maybe slide over the end of a screw.

have any ideals to how I can chech to make sure they are faulty???

 

[Mark_VTfisherman]

Re: How to check gages!

.....I started pulling wires out today! Seems like there was a good 10 miles of unused wiring in the boat....

This made me laugh.

I rewired a "big" 19' Mirrocraft for a friend last summer. The new wire came in one small-ish light weight plastic shopping bag from NAPA. On the boat, there was so much "extra" wire with unknown purposes that the trash bag of wire I pulled out was quite a bit heavier than the wire I put back in. Funny thing was, the new wiring had a lot more stuff hooked up to it than the old stuff- which was hodge-podge running everywhere and looping back apparently without any logical path. What I wound up with was probably just about what the boat came with OEM; everything worked that worked before, and the several items that did not work now worked. And all it took was wire cutters LOL

 

[JustJason]

Re: How to check gages!

Excuse me, but I've been building boats for 15 years

So for 15 years you haven't learned not to use wingnuts on a battery, and not to use a deep cycle as a starting battery yet???

How many starters and stators do you go through in a year?
Wouldn't hurt to put a fuse or a circuit breaker on that house power wire either.... coz nuthin says lovin like a 30 foot fuseable link.
Just sayin........





On to the gauges. Gauges are easy. They typically have 2 circuits.
1 is 12v in with ground for the lighting if the gauges are lit.
that takes care of the first circuit, doesn't matter if the lights work or not, identify it so you don't get confused.

The other is the gauges circuit itself. It's 12V in, ground, Input and/or output.
Verify that you have a 12VDC and a good path back to battery ground with little resistance.
After that, if its an output type gauge, like say a fuel level gauge, check for 5VDC on the output wire. If you have 12V to the gauge, and a good ground, and do not have 5VDC out then you have a bad gauge. If you do have 5VDC out then take that wire and touch it to ground. The gauge should go to full, if it does not the gauge is bad.
With an input type gauge, such as a tach. Check for power and ground. touch the input wire to ground and the needle should peg to the right, or max rpms in case of tach. if it does not then the gauge is bad.

 

[seabob4]

Re: How to check gages!

...So for 15 years you haven't learned not to use wingnuts on a battery, and not to use a deep cycle as a starting battery yet???

Sorry, this is not my boat, it is a customers. Therefore, that is the way he wants it. And there is now a 40A Bussman surface mount protecting the helm. I didn't have it when I took that pic...

That is very good TS advice you have given the OP. But one thing he should know, do not touch the pink wire (input) to 12V+, it will kill the sender...

 

[IWELD]

Re: How to check gages!

I found This Link to be really helpful to diagnose gauges while I had them out of the boat during reconstruction.

Thought it may help someone else.