temp gauge wiring

[iggyw1]

Hey guys,

I installed a head mounted temperature sender on my outboard motor and also a gauge in the dashboard that is calibrated to the sending unit. They are a matched set to go together. I have two seperate questions now:

1) I have to run one wire from the sending unit to the gauge. What sized wire would I need to run? It is a 12 volt system. The sender is on a 40 h.p Evinrude outboard, 1962 model.

2) Also, I am wiring the gauge directly to the ignition switch so it will turn off when the key is off. Do I need to install an in line fuse going to the temp gauge or is the ignition switch already fused? If I need an in line fuse, what size of a fuse would be required?
Thanks for any info you can give me!
IGGY

 

[F_R]

Re: temp gauge wiring

You don't need a very heavy wire to carry the current, even 20 ga or so will do it. However for mechanical durability, I wouldn't use anything smaller than 16 ga. Little skinny wires is so easy to snag and damage or corrode through. The larger diameter won't effect the operation of the gauge at all.

I'm not 100% sure, but the motor probably isn't fused. If it is, it is a 20 amp. It wouldn't hurt to install an in-line one with your gauge anyway. 5 amp would be plenty.

DO NOT ground your gauge to the black wires at the ignition switch. Those go to the ignition coils, and sending power to them will destroy them, in addition to making it run lousy. I think there is a grey tachometer ground wire in the harness. If so, you can ground your gauge to that.

EDIT: I just checked the wiring diagram for your motor. Is it safe to assume you have the original wiring harness and junction box? If so, there is no fuse in the ignition switch feed. Also, there is a 10 ga brown wire in the harness for the generator kit. If you do not have the generator, you can use that wire for your temp gauge and save running another. And yes, it has the grey tachometer ground wire in the harness.

 

[iggyw1]

Re: temp gauge wiring

You don't need a very heavy wire to carry the current, even 20 ga or so will do it. However for mechanical durability, I wouldn't use anything smaller than 16 ga. Little skinny wires is so easy to snag and damage or corrode through. The larger diameter won't effect the operation of the gauge at all.

I'm not 100% sure, but the motor probably isn't fused. If it is, it is a 20 amp. It wouldn't hurt to install an in-line one with your gauge anyway. 5 amp would be plenty.

DO NOT ground your gauge to the black wires at the ignition switch. Those go to the ignition coils, and sending power to them will destroy them, in addition to making it run lousy. I think there is a grey tachometer ground wire in the harness. If so, you can ground your gauge to that.

EDIT: I just checked the wiring diagram for your motor. Is it safe to assume you have the original wiring harness and junction box? If so, there is no fuse in the ignition switch feed. Also, there is a 10 ga brown wire in the harness for the generator kit. If you do not have the generator, you can use that wire for your temp gauge and save running another. And yes, it has the grey tachometer ground wire in the harness.

Thanks for your help. Yes, I do have the generator on my motor, but I also have a ground right from the battery that I brought up to the front of my boat as I also installed a fuse block up front ('hot' from the battery as well) for the radio, the spotlight, the horn etc., so I will hook up the power for the temp gauge to the ign. switch and ground it to the ground that I put in previously. I want the temp gauge to go off with the key, or I would have put it directly on the fuse block that I put in. If I did that, I would
need an off/on switch for the gauge and to me that isn't a good idea. I will add the in-line fuse for the gauge too as you suggested. I know what you mean about too thin of wire. It would break too easy if snagged with something. Thanks again.

ALSO, I see by your reply to me that I should not have used the ground at the ignition switch for my VHF radio that I installed today. I will take that ground off of the ign switch and ground it at the fuse block ground that I put in directly from the battery. I do not want to ruin my coils. Thanks.