How do you install an ammeter - layman language

[Realdon]

I almost feel guilty asking so many questions but the answers are normally super thus these forums are "Boating 101" for me.

From my previous searches I know that a lot of individuals will tell me to install a voltage meter instead of an ammeter but I have my reasons for the ammeter and they are as follows:

1.) I made a new dash and left a hole for an ammeter.
2.) I have a new ammeter.
3.) I already have installed a voltage meter.
4.) I am old enough to remember when cars had ammeters.

So unless you can think of different and useful 2" meter to put in place of the ammeter I am going to install it whether it works or not just for decor.

Now that I have that out of the way, how do I install an ammeter on a 1993 Mercury 150hp 2.5 Litre XR6 motor? The terminals on the meter are marked "S", "I", & "G". The "G" is obviously for ground and the "I" is possibly for Ignition but I don't have a clue for the "S" is for. Can anyone tell me where to find the correct wires to connect to the ammeter?

Oh yeah, I am not in a position to start the motor to see if the gauge works or not.

You clear and concise instructions would be greatly appreciated.

Don

 

[Barnacle_Bill]

Re: How do you install an ammeter - layman language

Since you already have a voltage gauge why don't you install something more useful like a water pressure or temperature gauge.

 

[Realdon]

Re: How do you install an ammeter - layman language

Since you already have a voltage gauge why don't you install something more useful like a water pressure or temperature gauge.

Well, I already have a water pressure gauge (although I have no clue what good it is) and I can't imagine why I need a temperature gauge. BTW, the temperature of what?

No matter if it is actually needed or even useful, I do want to install the ammeter because I have both it and the hole for it. I would really like to know if it also needs a shunt to be installed.

Cheers,

Don

 

[Chris1956]

Re: How do you install an ammeter - layman language

Don, You would need to run two heavy gauge wires from the voltage regulators to the ammeter. The ammeter must be in series with the charging wire to the battery. A voltmeter will tell you if the motor is charging, and is a whole lot less work and is safer.

 

[Realdon]

Re: How do you install an ammeter - layman language

Don, You would need to run two heavy gauge wires from the voltage regulators to the ammeter. The ammeter must be in series with the charging wire to the battery. A voltmeter will tell you if the motor is charging, and is a whole lot less work and is safer.

Shouldn't one of those wires already becoming to the ignition?

Don

 

[DianneB]

Re: How do you install an ammeter - layman language

Can you tell us who's ammeter you have?

I am fairly knowledgeable about electrical stuff and I would expect an ammeter to have either 2 terminals (+ and -) or 4 terminals if it contains a lamp for night use but THREE terminals is MOST unusual.

Typically, in an automotive application, the ammeter minus terminal connects directly to the battery positive terminal. (The only thing that DOESN'T go through the ammeter is the heavy cable to the starter solenoid - ammeters can't handle starter current!) Everything else connects to the ammeter positive terminal - all electrical loads, the alternator, etc. In this arrangement the ammeter reads positive (+) if the battery is being charged or negative (-) if there is a current drain from the battery.

If you could clarify the make and model of the ammeter I might be able to figure out WHY it has 3 terminals

 

[Silvertip]

Re: How do you install an ammeter - layman language

You really don't understand how an ammeter works or what it tells you. A voltmeter for example is installed ACROSS the electrical system and it obviously measures system voltage. Anything above 12.6 volts means the system is charging. It does not require heavy gauge wires because there is little current flowing through it. An ammeter on the other hand measures the TOTAL CURRENT flowing to the battery from the charging system (a positive reading on the gauge) whereas a discharge from the battery (a negative reading on the gauge) means the charging system may be working but the "draw" from accessories is greater than the "output" of the charging system, or that the system simply isn't working. So -- the charging wire (red wire on the starter solenoid) must be disconnected and a larger run from that wire to the gauge, then from the gauge all the way back to where the red wire was connected to begin with. These two wires therefore carry the entire electrical load (charge -- to the battery, and discharge -- from the battery). If you have a new gauge the instructions will tell you how to wire it. Normally however, an ammeter has three terminals but they are IN - OUT and LIGHT. And NO -- you don't wire it to the ignition switch. Next, are you certain you have an ammeter (reads -20 -- 0 -- +20) or something similar. If it reads 0 - 16 or similar, you have a voltmeter.

Now then -- Temperature of what?? For heavens sake, you have an engine. Engines can get hot and overheat for a number of reasons and be destroyed in the process. Don't you think the temperature gauge would be just a bit more valuable than a rediculous ammeter?
Water pressure gauges measure the output pressure of the water pump. You install a new impeller when you install the guage. Note the idle, mid range and wide open throttle pressure readings. Any deviation from those numbers down the line means the water pump needs service. The tell tale stream merely shows water is flowing. It does not indicate how much or at what pressure. Temp, WP, and voltmeters are a ton more useful than an ammeter and all are available in 2-inch sizes. Sorry if this sounded a little "terse" but this is exactly why car manufactuers installed "idiot lights". Owners didn't know what the gauges meant but they did seemingly understand that a red light was bad. But they ignored those too so there apparently is no help for those who fail to read.

 

[spdracr39]

Re: How do you install an ammeter - layman language

Doesn't the "S" probably stand for solenoid since you want the power to shut off with the key? Otherwise the battery will go dead after sitting.

 

[Realdon]

Re: How do you install an ammeter - layman language

You really don't understand how an ammeter works or what it tells you.

Excuse me, but I TOTALLY understand how an ammeter works and what it indicates, I just have never seen one marked the way this one is. And if you would have read all of my posts you would have read where I do have both a voltage meter and an ammeter. The voltage meter is hooked up and working fine, the ammeter is not currently hooked up.

Don

 

[Lyle29464]

Re: How do you install an ammeter - layman language

ok an old man story. Lots of the boats built in the very early days and up through the seventies had amp meters. The manufacture ran two large wires as other people posted. But they used the amp meter as a source for feeding the dash and almost everything electrical. If was not unusual to see the amp meter with 4 or 5 wires hooked to "EACH" side of it. Things you wanted to monitor with the engine off were hooked so you could read the draw. This was done on cars way back. As other posters have said it is silly to run the wires to install one. It is a long run and the wires needlessly carry a bunch of current. A dead short in your alternator will melt the insulation off the wires and everything that is touching them. This can cause big problems plus the line loss. I see nothing gained unless your restoring a classsic. If you see a perfectly restored stanly steamer going down the road it will have new disk brakes. ( just noticed it is a outboard, please disregard some of my crap.)

 

[Realdon]

Re: How do you install an ammeter - layman language

Can you tell us who's ammeter you have?

I am fairly knowledgeable about electrical stuff and I would expect an ammeter to have either 2 terminals (+ and -) or 4 terminals if it contains a lamp for night use but THREE terminals is MOST unusual.

Typically, in an automotive application, the ammeter minus terminal connects directly to the battery positive terminal. (The only thing that DOESN'T go through the ammeter is the heavy cable to the starter solenoid - ammeters can't handle starter current!) Everything else connects to the ammeter positive terminal - all electrical loads, the alternator, etc. In this arrangement the ammeter reads positive (+) if the battery is being charged or negative (-) if there is a current drain from the battery.

If you could clarify the make and model of the ammeter I might be able to figure out WHY it has 3 terminals

You are correct about my gauge actually having four terminals. The "I" terminal that I referred to is also marked "+" and the "S" terminal is also marked "-". Actually the "+" and "-" are down on the side rather than the back of the meter thus I simply never noticed them....sorry 'bout that. There is a light in the meter and one side of it is the "G" terminal that I mentioned and the other side is not an obvious terminal but rather a screw head where a hot wire must be placed under to light the bulb. This screw head is not common with anything except the one side of the bulb so again, it must be for the hot wire for the bulb.
The gauge is actually a model 79 90940 QUICKSILVER brand and can be seen at http://tinyurl.com/25g5oab on the Doug Russell Marine site or at http://tinyurl.com/23f6lqw on e-bay (much cheaper).

Thanks a bunch for your interest and also for clearing things up.

Don

 

[DianneB]

Re: How do you install an ammeter - layman language

Okay now it makes sense Don!

You have your + and - terminals so you should be all set. With only the starter solenoid (heavy wire) directly to the battery +, the ammeter - terminal can go to the battery + and everything else goes to the ammeter + terminal.

Depending on the distance between the alternator, battery, and ammeter you can get by with lighter wire. If you know your alternator's amperage rating, you can find charts on line to determine what size wire to use. If you don't know the rating (assuming we are talking an single inboard or IO) 50 Amps should be safe.

Happy wiring!

 

[rwidman]

Re: How do you install an ammeter - layman language

"How do you install an ammeter - layman language"

You install an ammeter in series with the circuit you want to measure the current in. That's "layman language".

 

[Silvertip]

Re: How do you install an ammeter - layman language

Also be aware that many gauges use the same plastic housing which contain common markings. Just because the marking is there does not mean that terminal needs to be used. I've seen lots of voltmeters for example, with an "S" terminal. That terminal is not used internally and only the "I" (switched +12 volts) and ground (-) are used. Add the light if it has one. Sorry about the "understanding ammeter" comment. But also understand that if one does not know about engine temperature and water pressure gauges and has to ask about how an ammeter is wired, then one can reasonably question whether said person really does understand its purpose and use. Peace. My feelings remain the same as all the others. Use the console space for a more useful gauge.

 

[boltonranger]

Re: How do you install an ammeter - layman language

-- Temperature of what?? For heavens sake, you have an engine. Engines can get hot and overheat for a number of reasons and be destroyed in the process. Don't you think the temperature gauge would be just a bit more valuable than a rediculous ammeter?
Water pressure gauges measure the output pressure of the water pump. You install a new impeller when you install the guage. Note the idle, mid range and wide open throttle pressure readings. Any deviation from those numbers down the line means the water pump needs service. The tell tale stream merely shows water is flowing. It does not indicate how much or at what pressure. Temp, WP, and voltmeters are a ton more useful than an ammeter and all are available in 2-inch sizes. Sorry if this sounded a little "terse" but this is exactly why car manufactuers installed "idiot lights". Owners didn't know what the gauges meant but they did seemingly understand that a red light was bad. But they ignored those too so there apparently is no help for those who fail to read.

POST OF THE DAY
'Tip You killed me with that one!
-br

 

[Realdon]

Re: How do you install an ammeter - layman language

Also be aware that many gauges use the same plastic housing which contain common markings. Just because the marking is there does not mean that terminal needs to be used. I've seen lots of voltmeters for example, with an "S" terminal. That terminal is not used internally and only the "I" (switched +12 volts) and ground (-) are used. Add the light if it has one. Sorry about the "understanding ammeter" comment. But also understand that if one does not know about engine temperature and water pressure gauges and has to ask about how an ammeter is wired, then one can reasonably question whether said person really does understand its purpose and use. Peace. My feelings remain the same as all the others. Use the console space for a more useful gauge.

The reason that I originally said "BTW, the temperature of what?" is because I had just removed a gauge and related sensor that told me the water temperature of the water the boat was traveling in. I did not see any use for it because my Humminbird would tell me that. Thus the question about "the temperature of what?

Okay, if a motor water temperature gauge is what you would recommend to fill my 2" hole then please enlighten about that gauge and related sending unit. My main question would be "does a 1993 150hp Mercury XR6 normally already have a sending unit or would I have to install one?" If installation is required, what does that involve?

Cheers,

Don

 

[fish_on_the_deck]

Re: How do you install an ammeter - layman language

uh... dont ammeters have senders? It seems like everyone is saying above that you have to run the full cranking current from batteries aft, forward to ammeter in console, then back to the engine aft again?? which I agree would be a bad idea.

http://www.deltecco.com/ (google search for "dc shunt ammeter sender")

But dont most ammeters have a dc shunt resistive type sending unit? This would allow you to run two say... 16 or 18 AWG wires from the battery area to the gauge.

The eBay listing even says it has terminals for a "Sender". are we sure its not looking for a dc reisistance through a properly sized shunt? Obviously the "+" and "-" markings dont make munch sense then.

I would think you could tell by the terminals... if they are scrawny #8 terminals, then sender... if beefy 3/8" terminals then full current ammeter... whatcha got? could probably test with a correctly sized POT if you know what your doing?.

not an expert... just wondering...

 

[Silvertip]

Re: How do you install an ammeter - layman language

Any water temperature gauge for the engine requires one of two types of senders. For an outboard they are essentially a variable resistance that depending on water temp, presents 33 to 240 ohms to the "S" terminal on the temp gauge. Temp gauges also are of two types. One is calibrated C-N-H (cold, normal, hot) which is merely a relative indication. The other style of gauge is calibrated with actual numbers (60 - xxx or 100 - xxx). One style of sender screws into an unused port that enters the water jacket on the engine. the other type is a contact type that mounts under a head bolt and measure engine head temperature. The gauge has "I" (+12 volts with key on), "S" (the wire from the sender), ground, and "L" (internal light) connections. The guage and sender must match but are fairly universal for outboards. Don't know if your particular engine has a simple snap switch (on-off) temp sender or whether it is resistive. Water pressure gauges do not need a sender. They are nothing more than a pressure gauge with a small tube going to a vacant water jacket access port. Some installations can use a "T" fitting in the tell tale.

 

[DianneB]

Re: How do you install an ammeter - layman language

uh... dont ammeters have senders?

Not the inexpensive type of ammeter.

It seems like everyone is saying above that you have to run the full cranking current from batteries aft, forward to ammeter in console, then back to the engine aft again??

Read my post again. The starter current does NOT pass through the ammeter. Cranking current is so high that if the ammeter was sized for cranking current (200 or more amps) it would hardly move at normal charge and discharge currents.

The eBay listing even says it has terminals for a "Sender". are we sure its not looking for a dc reisistance through a properly sized shunt? Obviously the "+" and "-" markings dont make munch sense then.

Not true. even with a shunt type meter, which way you connect the sensor wires will determine whether the meter reads + for charge or - for charge.

 

[TerryMSU]

Re: How do you install an ammeter - layman language

Well I think all of you need to look at the E-Bay link he posted above.

The display clearly shows 50 (Amps, I assume). The text clearly says, "Gauge has threaded stud terminals for wiring - Ground, Ignition, Sender, plus an extra threaded stud for the gauge bracket".

Sounds to me like it might use a sender. The sender is what is often refered to as a shunt. A shunt is just a low value known resistance that creates a voltage drop across it proportional to the Current thru it. (Ohms Law for those who might have seen this elsewhere.) The meter then measures the voltage driop across that shunt. It is not clear to me exactly where the shunt is to be wired, but you must break the line, put in the shunt and then wire two wires from the shunt to the meter. My guess is that the shunt is in series with the ignition line. It might well be that this meter can handle the starter current. Again, we are still missing some information. If there is any doubt, just consider the size of wire to carry even 50 amps. Pretty big wire (Exact size depends on the length of the wire run). If it uses a sender, then the wire to the meter can be quite small.

Diane is correct on one point. The direction of the current will determine whether the meter reads plus or minus.

By the way, if there are two terminals for sender, I am certain that the sender can (and should be) remote to the gauge.

TerryMSU