Does my motor have an alternator?

Discussion in 'Boats and Motors' started by dshannon, Jun 12, 2008.

  1. This may seem to be a rookie question, and it is. 40HP Mercury 2 Stroke outboard. Taking a trip to Canada and I'm wondering if my battery will last a weeks worth of fishing? Thanks!!
  2. freyedknot

    freyedknot useless poster

    most likely it does. especially if it is electric start. how many wires hook up to your battery from the motor?

  3. Just two from what I can tell, The boat was wired by the previous owner. We have had the battery go dead once after only an hour of running the motor (charged all night). Made me wonder, only time thats happened?

    I'm gonna do some organizing here, I'll take a better looksee, thanks for the reply.
  4. I would think you have a short some where running the motor should not drain the battery. I think you have a wiring problem .do you have a bilge or aerator pump running all the time
  5. Always check the obvious first if you haven't and make sure your battery is good. That is exactly what a battery will do when on it's way out.
    If your battery is good - what Roger said.
  6. UFM82

    UFM82 The one others want to be

    But it will provide a charge. Most small outboards will run a magneto-based charging system that is underneath the flywheel. They'll put out about 6 amps or so. While this will charge a battery enough to start the engine on a regular basis, placing a load on the battery above the charging capability can result in a dead battery. Lights, bilge pumps, radios, etc can all draw power and eventually drain a battery. if you had yours go dead in an hour, I'd check the condition of the battery first. Then check the output of the engine. (When the engine is running touch a voltmeter probe to the battery terminals. You should see 13+ volts or better. If it reads 12.2 or less, it's not charging.) The voltage should also rise if you bring the RPM's up.

    As far as lasting a week in Canada? It should if everything is functioning normally. That's the tough part...


    Make sure you pack along a primer bulb. Those things are always going bad. :)