TOPIC: Wiring and fusing

I am in the process of replacing all the wiring, lights and accessories in my boat. I am actually going to go with pretty basic components, but NONE of the items I bought, show an amp. rating. Yes, they all have the voltage rating, but that is it. In the lighting, I can take them apart and check the bulbs to find the rating and add them up. On the accessories like the map light/lighter there is nothing. What is the usual amp load of this. I can't even find a rating in the catalogs. The lighter is so that I have the map light and a port to plug in a spot light. Even the spotlights in the catalogs will only show candlepower. Seems as if something is lacking in the selling of these items.

You don't mention if you have an existing engine-harness that has the wires for ignition switch, choke, starter solenoid, etc... or if you are rewiring all of that yourself. In that case- the GAUGE of the wire is more important.

I always go by automotive ratings. I use the same gauge wire (or bigger if i happen to have it) as autos would use for the same circuits.

1) Lights- Stern/Bow #14 to ea
2) Lighter(s) - #12 (I always wire in 2-lighters and hide one in the cabin or under the dash to protect from rain/splash etc.. This is for GPS/Cel-Phone etc...
3) Power from battery to main IGN switch- #10 (if not included in engine harness)
4) Power from IGN Switch to fuse-block for accessories only- #10
5) Power from BATTERY to fuse-block for "always hot" circuits- #10
6) Power from battery to HORN RELAY and Relay-to-Horn - #12 (or same as horn has on it now) (I mount the relay near the Horn)
7) Horn button/switch to HORN RELAY- #14 (activates relay only)
8) Tilt/Trim Pump- #10 (if not in harness) I also direct wire the tilt/trim to a 40AMP bi-directional momentary switch (have to hold it for it to work) mounted on/near the transom/splashwell. This really helps with trailer loading/unloading, working on the engine, etc..

Wires from the fuse-blocks to various accessories (dash/interior lights, fixed spotlight, depth/fish finder, etc.. should be the same or larger than the wires used on the accessory itself. Most single-circuit items will be #14 gauge. Things that draw alot of power use #12.

Thanks for the reply. The motor is a 35hp.,'57 Evinrude Big Twin with electric start. I do have the starter box that mounts on the stern and the harness that goes between it and the motor. There is no generating system on this motor, but I may change it in the future, but. YES, the amp. load determines the both wire ga. and the fuse size. Just very little information found on the loads of these components. I am really looking at the both the bow and stern navigation lights, 5 small courtesy lights under the deck, map light/lighter and powering the relays for the electric starter and electric choke. Thanks again for responding!

DaveK wrote:

I am really looking at the both the bow and stern navigation lights,

Use #14

5 small courtesy lights under the deck,

Use #14

map light/lighter

Use #12

and powering the relays for the electric starter

#14 to the "I" (sometimes "S") post on the solenoid is fine

and electric choke.

#14 is plenty

Agreed! And then select your fuse size to protect the wiring. Don't bother with the amp draw of the load.