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Boat Electrics


charlieannear
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Star Turn has a battery connected to the outboard, but it's not connected to anything else!

 

The last owner wasn't bothered apparently, but I obviously need to sort this out.

I'm fairly experienced with domestic and auto electrics, but my boat electrics knowledge is only recently learned from books.

 

What I would like to do is install a system that does the following.

 

Engine start battery

Deep cycle battery

Clever split charger

Distribution board (with circuit breakers?)

Switch panel for helm (not confident that existing one is any good)

 

Also needs the basics, i.e cable and battery clamps.

 

Does anyone have any advice on doing this?

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If you are experienced with auto elec, you'll do fine on the boat. They are both 12v.

 

The only main difference is that you can't use the boat body as a -ve, you will have to runn a -ve from the battery to the switch panel. You don't need circuit breaker, as the switch panel (should) have fuses. Othe elec equipments have additional inline fuses.

 

Depending what you do, you may or may not need a 2 battery setup. It will depends 1) on how many toys you are planning to installed. If all you will have is fishfinder and vhf, and the outboard is drawing small amount (what size is it anyway) 2) how long/much fishing you are planning. The longer you are anchored your ob won't be charging the battery, but you can switch the FF off, and use a backup handheld vhf, then 1 battery will probably be enough. It is also very easy to add an extra battery later, so there's no need to rush.

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I think having a look at one or two boats before I get stuck in is a good idea!

 

To answer Paul- I live in Parkstone.

 

Star Turn has a 50hp Johnson and the book says it puts out 12A.

 

Don't think there's much danger of drawing too much power even at anchor:

VHF transmitting on 25w can use about 5A

Chartplotter about 0.5A

Fishfinder about 0.5A

Lights (if I'm out in the dark, gulp!) won't use much either

Going to put in a car radio/cassette too, but that won't draw much current... unless I install a subwoofer!

 

But I like the security of 2 batts provides, running the toys from a deep cycle battery and always having a full one to start the engine. Don't want to have to use the pull start if I can help it!

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Charlie,

 

I completely re-wired BW last year and have the wiring diagram if you want it for ref - I have the set up you describe in your initial post.

 

Most of the bits you need can be either bought on-line (switch panel etc) or from auto shops - Halfords etc...

 

Planning is the key, then it shouldnt take more than a day from start to finish.

 

Let me know.

 

Adam

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Charlie

 

I'm clueless about electrics but I did have a chap rewire my boat which now has circuit breakers 2 bats and lots of toys. I live not to far from you. Your more than welcome to come and have a look at how this electrician did mine. I think it must be somewhere near how it should be as he fits the eletrics on larger craft for a living.

 

Pm me if your interested and I will send you my address

 

Martin

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Not sure why an earlier reply did not come through.

 

Try calling Matt Sydenham on 01202 707007

 

He runs an electronics company and is a Member

 

He has offered advice to Members on this subject from his broad experiances in the field of Marine Electronics.

 

Matt has offered this service regardless of wether you purchase from him, but he is able and willing to try and match prices. biggrin.gif

 

In my view its good to buy locally and support one of the major sponsors of our open competition. biggrin.gifbiggrin.gif

 

 

 

Matt has offered me the choice of 2 second hand radar units for the new boat

 

if anyone is interested in a 16 mile radar at a good price call matt or I

 

 

Cheers

Charlie

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  • 2 months later...
Charlie,

 

See the attached article. It contains most of what you want to know.

 

cheers

 

BF

Re-visiting this one...

 

With reference to the digram for two batteries and a 1/1&2/2/Off switch on Bob's document.

 

Please can anyone tell me the reasoning behind attaching the outboard cables directly to the battery, as opposed to connecting the outboard positive lead to the common terminal on the battery switch?

 

Wiring as the diagram illustrates means that the outboard always has electrical supply available even with the switch in the off position.

 

Wiring using the common terminal of the battery switch means that the outboard gets power from the source indicated on the switch, and if the switch is 'Off' the outboard is disconnected from the electrical supply.

 

Sorry if I'm being thick! ph34r.gif

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agree - and it also makes 9 under testing irrelevant on that set up.

 

finally you can't isolate battery A from the charging circuit so charging Bat B will always be dependant on the state of charge and potentially condition of A.

 

Looks like a slip up - aren't diagrams a wonderfull alternative to words!

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Charlie, Duncan, you are correct.

 

Interesting one isn't it?

 

This was actually done deliberately because of two experiences I have had of the battery switch failing. Once whilst on shore, but the worst one was whilst at sea drifting towards rocks!! Both times I was using a good quality switch.

 

With the switch wired as shown in the article you always have power to the motor if the switch fails. For me, on a small boat, this is more important than being able to isolate the battery from the motor. I don't think there is a safety issue with having the motor permanently connected to the battery on a small boat.

 

Which ever set up you use, I always tend to leave the battery switch in the BOTH postion when starting and running the motor. The only time I move the switch to BATTERY 2 is when fishing at night when I want to ensure I don't drain the engine battery (BATT 1).

 

With the switch in the BOTH position and the switch wired the conventional way, the charging to the batteries will be no different to the way I show it wired. The battery with the most demand will take priority on who gets the charge. Granted with the conventional set up you can isolate the charge to either battery, but I have never had a need to do this. Instead I feel much safer knowing that battery one is connected directly to the motor so that it will start.

 

I thnk this is a set up that works on a small boat, but wouldn't advocate it on a larger boat where the power demands are higher.

 

Having said all this, I'm going to change the article so that it shows the conventional set up. Getting tired trying to defend this set up. You'll just have to take the risk of the switch failing. blink.gif

 

cheers

 

BF

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Thanks again Bob.

 

I had read (in the 12 Volt Bible for Boats I think) that all switches sold bearing the 'CE' mark can be operated with the outboard running without the alternator field collapsing (that's only from memory but it was something like that rolleyes.gif ) I guess this relates to arcing/surges that might cause the damage that you describe.

 

What about turning it to 'off' as an emergency method of shutting off the motor? I can't see how this would cause any damage?

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What about turning it to 'off' as an emergency method of shutting off the motor? I can't see how this would cause any damage?

Turning the power off wouldn't turn off the outboard, unless you blow the rectifier and that in turn cause a fire the blow the engine..... dry.gif

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Charlie,

 

DO NOT TURN THE SWITCH TO OFF WHILST MOTOR IS RUNNING.

 

1 - Both - 2 - OFF switches can be turned from 1 to Both to 2 whilst running as there is always a current path to the battery.

 

However, if you switch to Off whilst the motor is running you will break the current path causing a huge leap in voltage to occur ( due to inductance ). The high voltage will potentially cause the rectifier diodes to be destroyed.

 

 

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First came across the perm outboard connection from iboats.com, the American use this set up a lot apparently, they also fit in an isolation switch between 2 way swtch and outboard just in case they want to disconnect it for any maintenence.

 

I have this set up and I think both set up has it own merit. I like mine cos I'm a dozy git and no doubt will one day turn switch to off by mistake while engine is running and blow the rectifier, plus most outboards have a tilt switch at the engine end, and if power is cut it won't operate.

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This'll teach me for trying to think too hard on a Friday afternoon... laugh.gif

 

But turning the switch to off is breaking the electrical circuit- that won't stop the motor?

An engine doesn't need elec to run once it's started, it get the elec straight from the alternaor/flywheel (that is if it needs elec at all, think off a 50hp pull start outboard, does it need elec?).

 

Been told by a Mercury mech switching power to off while engine is running will cost me a great sum to repair the retifier, don't try it unless your sister's/daugther's boyfriend is a marine mechanic and will do it for free.

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