Dear Kevin,

I am currently beginning my first boat wiring project, a total rewire of a small Owens cruiser from the late ’60s.

Here’s my problem:

The old wiring runs behind the original paneling and headliner. I could try dismantling everything to remove and replace the wires, but am concerned about damaging any of the woodwork. It’s old. It’s gorgeous. It would be a bitch to replace.

I don’t mind leaving the old wiring in place and just running a new harness, but that still leaves the problem of installing the new wires without causing any damage.

Any ideas?

RP

Dear Ron,

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Kevin.

Hi,

I was given your email address by a friend who highly reccomended you.

I’m just about to rewire my boat as it’s winter. There are a few things that I would like to know before I start.

What would you suggest as to the thickness of cable from the battery to the 6 gang switch panel? I’m only running the normal things:

• Fishfinder
• VHF radio
• CD player
• Bilge pump
• Lights
• Horn.

I am also wondering if I should put an inline fuse in the live cable between the battery and switch panel and what size fuse?

Any other advice you could give me on boat wiring would be much appreciated.

Many thanks for your help

Paul

Hi Paul,

I am posting a handy spreadsheet that will help you calculate all of your boat wiring sizes.

Once you fill in the blue boxes for total wire length, the sheet will calculate the correct wire size needed for each wire run and for your main panel feed.

You will want to put a fuse or circuit breaker as close as possible to the battery. The size of this will be dictated by the total draw of your panel (Cell C20)

Emergency devices (nav lights, horn, VHF radio, bilge pumps, and blower) are typically wired for 3% voltage drop.

All other devices are usually 10%. Some stereos cannot tolerate 10% and you will need to run them at 3%.

Please let me know if you have any questions,

Kevin

Hi Kevin,

I am having A very strange problem on my 72′ Sunseeker that I can’t figure out.

I recentlly replaced all the overhead lights throughout the whole boat with L.E.D. lights. All of the lights are powered by 24 volts and are wired in series. I used 12 volt L.E.D.’s throughout the entire boat and they work fine.

I then started on the exterior of the boat, replaced all the lights on the arch, aft deck courtesy lights and the flybridge courtesy lights and they too worked fine. Ok enough of all that.

Here is my problem, The last lights I tried to replace were the port and starbord gunnels, I have nine lights on each side and they are controled by separate switches. I installed all my new lights and they work great for a couple of minutes and then they start flickering and then they stop, and then they start again.

This is driving me crazy!

Can you please give me some insight as to why this is happening ?

Thank You,

Keith

Keith,

Without looking at the system, I would guess that your flickering lights are being caused by a voltage drop problem.

The LEDs turn off when the voltage drops too low. As soon as the current draw goes away (the lights turn off), the voltage rises again and the lights turn back on. This causes in increase in current, a voltage drop in the wire, and the lights turn back off again.

Increasing the size of the boat wiring at least one AWG will probably solve your problem.

It sounds like you have a wonderful boat. Can you send me pictures of your project that I can post on the site?

Thanks,

Kevin

Kevin,

I know little about boat wiring so please forgive my ignorance.

My brother has a 22 year old 17′ VIP inboard motor boat with an intermittent electrical problem. The navigation lights and bilge blower were not working.

While we were messing with it we quickly hit the trim switch to lower and raise the motor – immediately the navigation lights and blower started working.
Later, they stopped working and again we hit the trim switch to lower and raise the motor – again the lights and blower started working.

The boat wiring is generally not in good condition. There are splices in the wiring everywhere, but all the connections appear to be okay. The horn and the radio work fine all the time. The battery is good.

Any thoughts you have would be greatly appreciated.

Thanks,
Tim

Tim,

I would start at the battery and work my way to the components.

The common link between the engine trim, the blower, and the navigation lights is their ground system.

• Clean the battery connections. Replace wing nuts with locking nuts.
• Clean the ground connection on the motor – opposite end of negative battery cable. Ensure all connections are intact.
• Check the connections at the blower and lights to make sure they are intact and making good contact.

This should solve your problem,

Kevin