Outboard with an alternator

[Colin Morley]

Hi all you knowledgeable swallow boaters.
I have just acquired a Yamaha 4stroke 4HP outboard with an alternator. I liked the idea of an alternator because I have been frustrated by scrabbling around to get the battery out every day or two of sailing and charge it. I have had a 20 amp battery for a while but it still needs charging.
I have a Garmin chart plotter and depth sounder that works of the battery. There is nothing more frustrating than for the chart plotter to pack up just when one is negotiating a new place with shallows etc like Chichester harbour.

My plan is to use the motor to charge the battery, at least while the motor is running and for those times when I cannot afford to loose electricity.

The problem I now have an question for you is how to run the cable from the outboard to the battery in front of the centre board in a neat and seaman like fashion, or should I move the battery to a side locker nearer the motor and Chart plotter.

I could even have two batteries, one each side, then I might be able to run an autohelm because I often sail single handed.

[Tim Riley]

Colin,
I don't know anything about the Yamaha but it may turn out to be a dream rather than a reality. I have a Honda 5hp with an output but unless you are running at pretty good revs it does not make much power. Just pottering around did not do anything for me and I have found a couple of solar panels much more rewarding - keeps Garmin 551S happy all day long anyway!
cheers
Tim

[Rob Johnstone]

Hi Colin,

I think that you will find another problem with the output of the alternator. It is likely to be too uneven to provide a good charge to the battery and you will need to invest in some sort of charge controller. A good one will regulate both the voltage and the current delivered from the alternator to the battery.

You can probably find the right sort of thing on motorbike web sites......

Rob J

[Graham W]

Colin,

If you are concerned about battery longevity and capacity, have a look at this thread http://www.swallowyachtsassociation.org/smf/index.php/topic,881.0.html

Your 20Ah lead battery could be replaced with one of these, which because of the peculiarities of lithium, could give you nearly twice the autonomy that you have at present http://www.ebay.co.uk/itm/Ultra-Max-12v-20Ah-LiFePO4-18-Hole-Lithium-Golf-Trolley-Battery-/120901844487?_trksid=p2054897.l4275

If you stick with your lead battery and get a controller as Rob suggests, you could also use this to regulate the output from quite a large solar panel, giving yourself two charging sources.  You can also do the same for a lithium house battery but a suitable controller is quite a bit more expensive - so far anyway.