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Outboard charging circuit


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What's considered best practice for connecting the outboard's rectifier to the rest of the boat's wiring?

 

Occurs to me this isn't entirely straightforward because when the outboard's running _IT_ should be protected by a fuse; but even when it's not there's a live circuit to the tail with a connector right where it's subject to spray and other bad things.

 

 

 

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Read your outboard manual, or use a voltmeter. The charging circuit on many outboards is rectified (changed from AC to DC) but NOT regulated. DC Voltage will vary with revs. My 15hp merc can produce over 20v at full throttle. That would kill a battery pretty quickly if allowed to continue.

 

If your particular outboard is unregulated, and you are to use it for more than entering /leaving the marina, then I'd strongly suggest a fuse AND a regulator.

 

Not to do so will prematurely Kill the battery. It's like driving a car on flat tyres - it moves, but....

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As IT said the output may be rectified but probably not regulated. But at least on the older smallish outboards I am familiar with they are only capable of fairly low current output, enough to run a light or provide a trickle charge but no more. So they could be left charging a battery safely for hours.

If you connect a voltmeter to the terminals with nothing connected yes with some revs you will get over 20 volts, but with a load connected it is drops right back.

Do you have any details on the voltage and current output on your outboard?

Yes terminals should be protected from salt spray, and vibration causing chafing on wires.

 

There should always be a fuse in the circuit, ensure that the terminals are dc (some older ones had ac terminals and needed an external rectifier), then just connect it up and measure voltage with a digital voltmeter. 

I assume you are talking about a pull start axillary outboard. Modern electric start outboards have an alternator with much higher output ratings. 

 

One more note, you cannot use a regulator designed for solar panels to regulate the power from an outboard generator or alternator.

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Is it an F15C? If so, it has a rectified and regulated output already - seems most (all?) the new 4 stroke Yamahas have regulating rectifiers. !0amp circuit as you say, go ahead and connect it direct to battery, no problem.

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Hm, KM, 12.1 volts is about 25% charge. You should NEVER let a batt get below 50% if you want to get the best out of it.

 

Both current model Yamaha 9.9 4 strokes L and J models) have 12v 80w outputs - sorry that is only 6amps :-( Specs can be found here https://www.yamaha-motor.co.nz/products/marine-outboard/4-stroke-portable/13-ft99l

 

The reason you got that life from the battery is that it was not subject to much current when charging, and the charging was not for really long periods.

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