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

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Kevin.

Hello,

Please could you comment on the boat wiring diagram that I’ve drawn up.

It includes:

• Twin Verado outboards
• Shorepower
• Generator
• House batteries.

I’m currently trying to wire up a new boat here in Oman (no technical expertise available) and I’m really concerned about dangerous AC currents floating around the boat whilst my family swims.

Please could you have a look and give me your comments as I’m no expert at this?

I know that I’m missing an earth wire from the fused junction!

Any input from yourself will be most welcome.

Kind regards

Glyn

Hi Glyn,

Very nice diagram!

I have a few comments.

• Add circuit protection at the source of power for your 24 hour emergency bilge pumps fuse panel.
• Add circuit protection at the battery switch for your main DC distribution panel
• Your shore power ground (green) needs to run to your AC ground buss
• Your galvanic isolator is connected between your shore power inlet and the AC ground buss in the green wire

Also, I would consider not connecting the 3 bank inverter to all 3 banks. Instead,

1. Connect two legs to the house battery bank
2. Connect one leg to the port engine battery bank
3. Connect 0 legs to the starboard engine battery bank

This would allow you to completely drain your dc system with the inverter and still be able to start your starboard engine and charge the system through your automatic charge relay

As drawn, your boat’s AC electrical system should be shock proof.

Most marine AC problems occur when the DC ground is not connected to the AC ground. If you boat has an AC fault to a DC component, the common ground will allow the circuit protection on your AC distribution panel to trip and not energize the water below.

Please send me pictures of this project,

Kevin

Hello Kevin,

Thanks for your input.  I’ve updated the pdf (in case you want to use it)

I’ll take pics and send them to you. But, it might take a while as I’m in Oman and it’s a real struggle to source the various electrical components. Nevermind the marine grade wiring (at the local marina they have a bad habit of using domestic grade wiring).

That’s why I’ve elected to attempt all this myself.

Regards

Glyn

Hello:

I have a question and hope someone may be able to point me in the right direction.

I have a 1989 Maxum 2300SC. It originally had an 898 Mercruiser engine and Alpha 1 outdrive. I believe that would have been a 305 Chevrolet. I purchased the boat about one month ago and was told the engine is now a 350 that still has all the original 898 brackets etc…

The engine is fine. The outdrive is fine. My problem is in shifting. My shift cable to the outdrive is extremely easy to push and shift so it appears fine.

I have checked the “Shift Interrupter Switch” and it is disconnected. I would like to rewire the switch to make sure it is either good or bad then replace it.

My problem lies with the fact that the distributor has also been changed. It is no longer a Points type ignition. It has been replaced by a Chevy HEI ignition. Is there a difference in a stock HEI distributor and a marine distributor? Can I make mine work?

This being said, Can I rewire the switch to this distributor? If so how?

I have a white wire with green stripe connected to the switch but lying freely on the top of the manifold. Not sure where it went. Also have ground from switch disconnected but I see where it goes. I also understand that the old switch that I have is no longer made. If mine is bad, I will need to order a new replacement. If I have to have the replacement, can it be wired to this distributor?

Any help would be appreciated.

Thank you.

David

David,

Distributor and Starter

It is very important to determine if the HEI distributor is ignition protected. Most automotive systems are not. It needs to have a UL 1500 ignition protected (or equivalent) rating to be safe. If the previous owner installed a non-ignition protected distributor, I would also check the starter.

Shift Interrupter

Most shift interrupters worked off on the negative side of the coil. They would momentarily ground the coil and cause the engine to hesitate while shifting. Most automotive HEI ignitions do not give access to the negative side of the coil. They have a tachometer output that does not interrupt the engine ignition when it is grounded.

A Mercury Marine HEI ignition system from the same era would have a shift interrupter output.

Converting back to a coil system would give you a connecting point to the shift interrupter.

Thanks,

Kevin

Hi Kevin,

Why is there no requirement for starter motor over-current protection?

Would it not be a good idea to have a breaker or a (large) fuse in the heavy current side?

Apparently, marine wiring practice guidelines dictate that all 12 volt circuits except starter motor leads should be fused.

Regards

Russell

Russell,

The idea of over-current protection has been discussed for several years by the American Boat and Yacht Council’s Electrical Technical Committee. This group writes the standards to which most boats are built in the US. They have not decided on a practical solution to this problem.

Circuit protection as close as possible to the source of power is always the best practice. Unfortunately, starter motor over-current protection is not practical. Initial starter current is extremely high – amd with age, this current increases.

To prevent nuisance tripping, the typical fuse would need to several hundred amps. The average 2awg battery cable is rated at less than 200 amps.

On branch circuits, the fuse is sized to protect the device. The wire is sized to carry the current of the device or prevent a voltage drop; whichever dictates a larger wire.

Thank you for writing.

Kevin