getting dc from outboard

Discussion in 'Boat Design' started by carl mccall, Jul 12, 2009.

  1. carl mccall
    Joined: Jul 2009
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    carl mccall Junior Member

    not sure if this is the right place to ask but here it goes,i have a newer merc 8 hp 2 stroke,is there a way to get twelve volts dc out of motor
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    It depends on the motor, but you may have about 5 to 7 amps of 12 VDC output. Again, it depends on the model and how it's equipped. To be specific, you'll have to proved the year, model number, etc.
     
  3. carl mccall
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    carl mccall Junior Member

    serial#06218815,also another #on power head 0g218815,dont know exact year but it"s pretty new it was origunally kicker on sailboat
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The year is a significant issue, pre '97 or post '97, but I'm fairly sure you don't have any 12 VDC output. I'm assuming it's pre '97 by the number you provided. This engine has no rectifier or regulator shown in the usual parts availability lists, suggesting it doesn't produce DC other then firing the ignition system.
     
  5. Frosty

    Frosty Previous Member

    I saw a guy in a magazine fit an alternator upside down on top of the motor driven by a small v belt. Maybe he machined a groove in the flywheel, this would certainly give the RPM.

    He cut a hole in the cowling and boxed it in from the weather.
     
  6. carl mccall
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    carl mccall Junior Member

    hmmmmmmm!
     
  7. Frosty

    Frosty Previous Member

    How much power do you want? You can get small alternators 35amp.

    Or a small dc motor just turn it, it would be RPM sensitive though.

    Or real small bicycle generator with a rubber wheel on it!!!

    As I say depends on how much power you want.
     
  8. Guest625101138

    Guest625101138 Previous Member

    My Johnson 6HP long shaft had a socket on the side for power offtake. The motor was stolen many moons ago but I still have the plug. If it has electric offtake wouldn't it have a convenient external plug somewhere?

    If you are going to the trouble of making something then have a look at an outrunner motor for model aircraft. These have huge power density so you will get 200W from something that weighs very little and no brushes to worry about just a small 3-phase bridge on the electrical side and a rubber tire spring loaded against the flywheel - maybe a little toothed belt if you want to do it properly.

    Do any bikes have separate little aternator?

    Best bet may be a portable generator. I have seen 1000W units for AUD98 at the local hardware. Will serve many purposes. A plug in battery charger for another AUD20.


    Rick W
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    If there was a 12V socket, Carl Mccall wouldn't have posted the question or he is a total a*****e.
    I assume that he isn't.

    Getting 12VDC from the outboard means pulling the flywheel, installing the proper coil in the empty space opposite the ignition coil and screwing a bridge rectifier against the side of the engine that already has a hole for that purpose.
    The coil can be ordered from Mercury as a (quite expensive) spare part or from a motorcycle shop. The inside diameter of the flywheel is the only constraint, all 12V coils are of the same construction.
     
  10. Guest625101138

    Guest625101138 Previous Member

    The first thing any smart electrical repairer will ask is "Is it plugged in and turned on?" When they say "yes of course". His response will be "can you indulge me and check right now - is the correct plug in and is the switch turned - now get another appliance and test the outlet."

    In fault finding in many years in operational roles I learnt to never assume anything. Also never dismiss any observation because you believe it cannot happen. Every observation is valid. I sometimes found it was my inability to correctly interpret the observation was the limitation, not the observation being wrong.

    Rick W
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I've made plenty of money walking into a customer's home and flipping a breaker back on.
     
  12. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    That sounds like a job of my life. My compliments. :D
     

  13. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    assumption is the mother of all f**kups"...

    The little gasoline 1000w generator seems to be the cheapest and easiest way out with juice to spare
     
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