Adding an Ammeter to an Outboard

[Hydro Mark]

Hello,

I have a small Glassic runabout that I'm restoring and it has a Merc 1250 outboard. Since I've been unable to find a voltmeter to match my vintage gauge set, I'm going to install the matching ammeter that I have. I'm also taking the opportunity fuse everything I can, add a battery shut-off switch and re-wire the boat harness - the wires fell apart when I took the "Mercontrol" apart.

This is how I planned on hooking it up and I was wondering if it is correct and I'm confused about a couple of things:

1) Should I put a fuse in the alternator wire?
2) Is 10ga wire large enough for alternator wire?
3) The Salmon-colored wire doesn't appear to go to anything? Can I abandon it?



Thank you to anybody that can help me,

Mark

 

[gm280]

Re: Adding an Ammeter to an Outboard

Hello,

I have a small Glassic runabout that I'm restoring and it has a Merc 1250 outboard. Since I've been unable to find a voltmeter to match my vintage gauge set, I'm going to install the matching ammeter that I have. I'm also taking the opportunity fuse everything I can, add a battery shut-off switch and re-wire the boat harness - the wires fell apart when I took the "Mercontrol" apart.

This is how I planned on hooking it up and I was wondering if it is correct and I'm confused about a couple of things:

1) Should I put a fuse in the alternator wire?
2) Is 10ga wire large enough for alternator wire?
3) The Salmon-colored wire doesn't appear to go to anything? Can I abandon it?


Thank you to anybody that can help me,

Mark

Okay I see you know that Amp meters work differently than simple volt meters. That being everything has to run through the amp meter for it to register the current being used. And you also have to know that any current meter doesn't pass all the current through the actual meter but through a shunt and only a very small portion is channeled through the meter itself. So with that being known, I would install the current meter or the shunt at the battery itself and then just run smaller wires to the meter at the control panel or helm. Otherwise you will have to run very large wire from the battery through the meter and then to the accessories... So look for a shunt for the max current you will use and get one to install at the battery. That will be a lot simpler and cost so much less then installing such large wires...

 

[Don S]

Re: Adding an Ammeter to an Outboard

Why not just use a Voltmeter? it will tell you basically the same thing, if your charging system is working or not.

Marine gave up ammeters back in the early 70's.

 

[Hydro Mark]

Re: Adding an Ammeter to an Outboard

Thanks for the replies. I am restoring a 50's-60's style runabout and have a matching, vintage gauge set.

GM - The ammeter I have has an internal shunt. The run from the motor to the gauge is approx 15'. Is 10ga sufficient?

Don - The reason I'm not using a voltmeter is because I have been unable to find one that matches. The gauges have a design on the face and I want them to match.

Thanks again,
Mark

 

[gm280]

Re: Adding an Ammeter to an Outboard

Thanks for the replies. I am restoring a 50's-60's style runabout and have a matching, vintage gauge set.

GM - The ammeter I have has an internal shunt. The run from the motor to the gauge is approx 15'. Is 10ga sufficient?

Don - The reason I'm not using a voltmeter is because I have been unable to find one that matches. The gauges have a design on the face and I want them to match.

Thanks again,
Mark

Mark, 10 gauge wire really depends on how much current will be running through the meter. Being how the shunt is inside your meter, then you are stuck with that option. So figure out the total current the meter can display and then use a wire gauge chart to purchase the correct gauge wire to cover the current for that run and distance. The real problem I see is the distances. The further the run the heavier gauge you will need. 10 gauge may do, just depends on your setup...

 

[Hydro Mark]

Re: Adding an Ammeter to an Outboard

Mark, 10 gauge wire really depends on how much current will be running through the meter. Being how the shunt is inside your meter, then you are stuck with that option. So figure out the total current the meter can display and then use a wire gauge chart to purchase the correct gauge wire to cover the current for that run and distance. The real problem I see is the distances. The further the run the heavier gauge you will need. 10 gauge may do, just depends on your setup...

Thanks GM. I have not idea how much my alternator puts out. As for the load, nav/inst lights, horn, 12v outlet and ignition. Ignition is another one I have not idea how much it draws. I will probably add a stereo at some point, but I can always add a separate run if I have to.

Thanks again,
Mark

 

[gm280]

Re: Adding an Ammeter to an Outboard

Thanks GM. I have not idea how much my alternator puts out. As for the load, nav/inst lights, horn, 12v outlet and ignition. Ignition is another one I have not idea how much it draws. I will probably add a stereo at some point, but I can always add a separate run if I have to.

Thanks again,
Mark

Mark what is the maximum current your meter can read (e.i. it reads 40 amps max reading). That will be your current to decide the wire size. Make sure that wire run is fused or circuit breakered as well...safety first...

 

[Hydro Mark]

Re: Adding an Ammeter to an Outboard

Mark what is the maximum current your meter can read (e.i. it reads 40 amps max reading). That will be your current to decide the wire size. Make sure that wire run is fused or circuit breakered as well...safety first...

The meter is a 50-0-50 but it probably came from an inboard as I don't think outboard had an ammeter at the time.

 

[gm280]

Re: Adding an Ammeter to an Outboard

The meter is a 50-0-50 but it probably came from an inboard as I don't think outboard had an ammeter at the time.

Okay, I personally don't think you will ever read 50 amps on your setup, so if you make a conscience decision to go for 30 amps or even 20 amps, then make sure the wire choice can handle that and fuse or circuit breaker for that amount too... It is that simple... Don’t worry about the engine output because I don’t think you will ever see 50 amps ever coming from your engine... You will be lucky to see 20 amps unless you have a huge alternator on it... Just sum up the total amps that you think you will see across the meter and make that your fuse/breaker and wire size choices... If your lights run 5 amps and your radio is 10 amps and your bilge pump is 3 amps, add them all up and wire and fuse/breaker for those maxes...maybe add a few amps for safety as well...

Hope that is helpful and understandable too...

 

[Hydro Mark]

Re: Adding an Ammeter to an Outboard

Okay, I personally don't think you will ever read 50 amps on your setup, so if you make a conscience decision to go for 30 amps or even 20 amps, then make sure the wire choice can handle that and fuse or circuit breaker for that amount too... It is that simple... Don’t worry about the engine output because I don’t think you will ever see 50 amps ever coming from your engine... You will be lucky to see 20 amps unless you have a huge alternator on it... Just sum up the total amps that you think you will see across the meter and make that your fuse/breaker and wire size choices... If your lights run 5 amps and your radio is 10 amps and your bilge pump is 3 amps, add them all up and wire and fuse/breaker for those maxes...maybe add a few amps for safety as well...

Hope that is helpful and understandable too...

Got it. Thanks GM!

Mark

 

[Boatist]

Re: Adding an Ammeter to an Outboard

If you put a fuse in the line between the alternator and the battery which I would not recommend put in a very high amperage one. Bottom line if the fuse blows or the battery cable comes loose it usually destroys the alternators output diode block. It has the same effect as turning on the battery switch off with the engine running.
I understand why you want a amp meter but a volt meter gives you much better information without the risk of blowing your alternator.

 

[Boatist]

Re: Adding an Ammeter to an Outboard

If you put a fuse in the line between the alternator and the battery which I would not recommend put in a very high amperage one. Bottom line if the fuse blows or the battery cable comes loose it usually destroys the alternators Output diode block. It has the same effect as turning on the battery switch off with the engine running.
I understand why you want a amp meter but a volt meter gives you much better information without the risk of blowing your alternator.

 

[Hydro Mark]

Re: Adding an Ammeter to an Outboard

If you put a fuse in the line between the alternator and the battery which I would not recommend put in a very high amperage one. Bottom line if the fuse blows or the battery cable comes loose it usually destroys the alternators Output diode block. It has the same effect as turning on the battery switch off with the engine running.
I understand why you want a amp meter but a volt meter gives you much better information without the risk of blowing your alternator.

Boatist- Thank you. I've decided to not put a fuse in. I am constantly looking for a voltmeter, and when I find one that matches, I will replace the ammeter with it.

Thanks again,

Mark

 

[skyboy2410]

Re: Adding an Ammeter to an Outboard

This post has been very helpful, as I was going to install an ammeter myself. Steve