Charge battery with outboard engine?

On my Mercury 4 HP fourstroke I see a connection between the stop button and the fuel connection. Can this be used to connect to the battery to charge it? Anyone with experience?

A 4 HP engine does not have an alternator (dynamo) but a 'charge coil' (laadspoel, not sure about the correct translation). This does give a bit of power, however the current is so limited that charging a battery is going to take hours and hours - if you even get it charged at all.
Most often it's not found on engines < 8 HP. You should be able to use it for charging cellphones etc. So if there were a connection on my Yamaha 4hp I'd probably hook it up.

Hallo Rene,

thanks for your feedback. I will look for another way to charge my battery.

Hi Henk,

I have a full explanation of the system I use at:
http://www.seahawk17.org.uk/boatshed/bss.htm#electrics

Hi Henk,
Maybe it will be helpful if you give an idea about what you are going to run off the battery. If it's an occasional led light a solar panel like Greg described (possibly in combination with the coil in your outboard) will be sufficient.
Also to take into consideration:
- The number of hours of motoring. If you are using your engine for 15 minutes I wouldn't even go to trouble to wire a battery from the engine.
- Are you going to leave the boat in the water during the season? Or taking day/weekend trips and then taking the boat back home. In our case the investment of the solar panel wasn't worth it and just hooking the battery up overnight on the mains was much simpler.

Thanks Greg,

it is great to see how helpfull the community is.

We use our battery for navigation lights and occasional cabin lighting.  It's charged from a small flexible solar panel (about 60 x 30 though the solar area is smaller) which is permanently fixed on with elastic just above the tiller.  We never need to charge the battery with anything else.

Victoria (Marsh Marigold)

Sent from my iPad

I know this post is quite old now, but an article on charging batteries from outboard lighting coils can be found in PBO No.530 dated January 2011. Basically, the content suggests that the coil on the flywheel is to provide current for nav. lights (The current is A.C.) so if you want to charge a battery you have to purchase a charger to provide D.C. Usually this has only one diode and therefore only offers half the A.C. sine wave (ie half the available power). Using a bridge rectifier, capacitors and a switch, the author obtained dual charging rates of 13.2v @ 8amps and over 14 volts, at 4 amps. The circuit costs less than a tenner using bits from Maplin's. Full diagrams accompany the article. I'm not sure where we stand with copyright, but if you have difficulty finding the article through PBO, I have still got mine!