Basic Wiring Project

[RudeEvin]

I have a 1967 Evinrude Sport 16 with a 1978 evinrude 85hp outboard. I am trying to reconnect some wiring that was disconnected/abandoned before I took ownership of the boat. Specifically, I am trying to connect the voltmeter, the "ON" light (to show that the engine is running), and the "Hot" light to show overheating. I do have the original service manual which includes a nice wiring diagram. The problem is that it does not show any voltmeter or display lights. I'd rather get some advice instead of shorting something.

The voltmeter only has two posts, one labeled "ENG" and the other labeled "BAT". At first I thought it would be a negative and positive type connections, but then I thought that maybe it is an in-line positive wiring set-up. There are no other grounding posts or screws.

The display lights are simple and both have positive and negative connectors. There is a warning buzzer/horn that sounds when the engine overheats. It does work, and I assume I tap into the wire connecting it to the engine.

Any ideas?

 

[NYBo]

Re: Basic Wiring Project

Voltmeters are hooked to negative and positive battery leads. For the positive (most likely the ENG terminal on yours), the usual practice is to tap into the accessory terminal on the ignition switch. If you already have other instruments that operate when you turn on the ignition, you can daisy chain off the nearest one.

You can probably hook the HOT light in parallel with the warning buzzer.

A tachometer is even better than an ON light.

 

[Silvertip]

Re: Basic Wiring Project

I'm betting that due to the age of the boat that is NOT a VOLTMETER but rather an AMMETER and I base that on the terminal labels. Voltmeters have IGNITION and GROUND connections. AMMETERS have LINE and LOAD connections as they are a "series" connected device inserted into the main power distribution wire. The key to all of this is to look at the gauge. If the numbers read -30 - 0 - +30 or something similar you have an AMMETER. if the numbers read 0 - 18 or 10 - 18 or something similar you have a VOLTMETER.

 

[RudeEvin]

Re: Basic Wiring Project

I'm betting that due to the age of the boat that is NOT a VOLTMETER but rather an AMMETER and I base that on the terminal labels. Voltmeters have IGNITION and GROUND connections. AMMETERS have LINE and LOAD connections as they are a "series" connected device inserted into the main power distribution wire. The key to all of this is to look at the gauge. If the numbers read -30 - 0 - +30 or something similar you have an AMMETER. if the numbers read 0 - 18 or 10 - 18 or something similar you have a VOLTMETER.

I stand corrected. Per your description, I must have an ammeter because it shows -15 / 0 / +15. You mention the "main power distribution wire", is this the power coming from the engine alternator? I'll have to check my wiring diagram. That would connect to the "ENG" post on the ammeter before the ignition switch? How do I connect the "BAT" post on the ammeter, i.e. where does it go after the ammeter?

With regards to the temp sensor wire, is it a ground that is accuated when the sensor gets too hot? I want to make sure I hook up the "HOT" light to the proper terminals.

With regards to the "ON" light, what wire should I connect it to to show only when the engine is running? It's an idiot light, but I just want to make it work rather than have a dead display on the dash.

 

[metriccrescentwrench]

Re: Basic Wiring Project

AMMETERS have LINE and LOAD connections as they are a "series" connected device inserted into the main power distribution wire.

Good catch on the gauge in question being an ammeter. As far as hooking it up, I'm pretty sure that there should be a shunt resistor somewhere in line between the battery and engine, and that two wires come forward to the gauge from that shunt resistor. SO.... if somebody's removed that you'd be out of luck as far as simply connecting wires to the ammeter and having it work.

 

[RudeEvin]

Re: Basic Wiring Project

Shunt resistor? Can't say as I have ever heard of one of those. Ok, so I want to make sure I have this correct, the main power cable that connects to the battery and engine needs to have a shunt resistor spliced in? Does this resistor have two connectors that allow me to run a baterry side and engine side connection? Sounds simple enough. Are shunt resistors engine or ammeter specific? Thanks for the info. I'll start searching for shunt resistors.

 

[RudeEvin]

Re: Basic Wiring Project

I did some research and now it makes sense regarding the need for a shunt. Now my question is whether my ammeter has a built in shunt. Only I can answer that, ut I must check to see if I can get a model/name info. I did test the ammeter by using a 12v charger and a 12v battery. I took the charger and attached the negative clamp directly to the battery's negative post. I took the positive clamp and put it on the "ENG" post of the ammeter and ran a jumper from the "BAT" post on the ammeter to the postive post on the battery. The meter registered about 10 amps. I don't remember the amp rating of my charger, but it one of the small slow charge type, about the size of a shoe box. I thought it was registering 10 volts, but now I know it is an ammeter, so it must be amps. Does this type of reading mean that the ammeter has a built in shunt? If so, is there a way of tapping into the accessory power off the ignition or do I have to splice into the main cable running from the battery to the engine?

 

[Stamey]

Re: Basic Wiring Project

You may want to research the ammeter itself as it is probably some universal gauge, not specific to any boat or engine brand.
http://www.rc-electronics-usa.com/current-shunt.html

Chris

 

[RudeEvin]

Re: Basic Wiring Project

Thanks for the info, I will check it out. I would also like to find a wiring diagram so I know I am wiring it correctly. My manual does not have it. I'm sure I can find something on-line. It sounds simple, but the last thing I want to do is short something out, especially right before going on vacation.

 

[RudeEvin]

Re: Basic Wiring Project

I found the manufacturer of my ammeter, Stewart Warner, and they are pretty sure the unit has a built in shunt. They had a hard time finding info because this unit is from 1966. So basically I need to tap into the charging wire. Is this the red wire off of my rectifier, i.e. the one that goes back to the starter/battery? My diagram shows this wire leaving the rectifier and going back to the a terminal on the starter, which in turn also runs a fused line up to the ignition switch. Does this description give enough info for someone to help give advice? Thanks in advance.