Wiring problems need help

we are trying to wire the bow and transom lights and plug in for spotlight in our boat. When we run them directly from the battery they work fine but when we try to run them thru the on off switch the wiring from the battery to the switch gets hot and starts melting.I am using the switch recommended by the dealer and 14 or 16 ga.wire.The dealer said we need to ground each light and the plug but I dont know why we should have to ground them just because of the switch.Also once these are working i will run a inline fuse between the battery and switch.Thanks for any help

Forgot to say this is only 12 volt

Your first comment about not needing to ground them because of the switch is puzzling.

The switch breaks the positive wire. The ground never goes to the switch unless it's used for a lighted switch. The ground goes directly to the negative lead of the light. The positive goes to one lug of the switch, then you wire from the other lug of the switch to the positive wire on the light.

Do you know how many amps the spotlight draws and how many amps the switch is rated for? Sounds like you need a higher rated switch.

What CatFan said.

Sounds like you switching power to ground somehow if your wires melt.

Barnacle Bill thats what i was originally thinking but i think catfan and cane pole are right now that I think about it. As soon as i get home later i am going to check I think we ran the ground to the switch also and I dont want to do this.Am I correct on this?And thanks for the help I appreciate it.

Yeah, I misread your post and thought you said the switch was melting. If you ran a ground to the switch along with the positive wires then that is definitely your problem. You should replace those burnt wires and make sure it is fused as close to the battery as possible.

We got the lights wired.What we had done was run both the pos. and neg.wires to the switch.Thanks again for the help.