Alternators

Discussion in 'Sterndrives' started by Art1848, Jul 6, 2016.

  1. Art1848
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    Art1848 Junior Member

    Is there a way to tell a Marine alternator from an auto alternator by looking at it? Not sure what is on the engine I'm working on. It' a Delco-Remy.
     
  2. Ike
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    Ike Senior Member

    Not necessarily. But if the alternator has any openings or vents on it, to be marine there will be flame screens on the openings. If it has no openings or vents, is it sealed?

    the major difference between auto and marine alternators is that marine alternators are required to be "ignition protected" That means, should there be fuel vapor in the engine compartment, the alternator cannot set it off if the alternator makes a spark. Usually these sparks come from brushes inside the alternator, but these days there are alternators that have no brushes. They use different types of contacts and do not spark.

    Generally there is a label on the alternator or on the box that says Complies with 33 CFR 183. 410 or it may say UL Marine Listed.

    If there is a specific alternator in mind, the best thing to do is contact the manufacturer, give them the model number and ask if it is "marine".
     
  3. Ike
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    Ike Senior Member

    Got any pictures of the alternator in question?
     
  4. Art1848
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    Art1848 Junior Member

    Will see what I can do about pics. I have a feeling someone went the cheap route and put a auto one on. Can not find a model # on it.
    I need to do what's right and safe.
     
  5. Ike
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    Ike Senior Member

    Replace it. It's not worth your life.
     
  6. Ike
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    Ike Senior Member

    This is a Delco Remy Marine alternator. You can see the screens on the back.

    [​IMG]
     
  7. CDK
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    CDK retired engineer

    The main difference is the price tag. Take a $150 automotive alternator, add a $1.50 wire mesh screen and you have a $450 marine one.
    I've always wondered why the screen is always only on one side. Alternators have brushes on solid copper rings so sparks are virtually impossible.

    But if you want to be absolutely sure, use an alternator for a military vehicle, they have screens on both sides....
     
  8. Ike
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    Ike Senior Member

    Why only screens on the back? air is being sucked in the front. If there is an explosive mixture in the engine compartment, it is sucked in the front. If it is then ignited by a spark the flame front goes out the back. The screens cool the flame front to the point that it will not ignite the vapors outside of the alternator. The pressure differential keeps it from going back out the front.

    Ignition protected equipment are not "explosion proof" which is a much higher level (and even more expensive) as they are required to be on aircraft, or electric pumps on gas pumps. Why screens on both sides on military vehicles? I can only guess but considering the environment they have to work in I would venture it is to keep stuff out.

    And the old why so expensive question? Frankly it's mostly due to volume. Auto alternators are made by the millions and millions and distributed through auto dealer and parts stores world wide. The shear volume lowers the per unit cost (I remember buying a new alternator in 1970 for $60.00) There are literally millions of these outlets.

    Marine alternators however are made in much smaller volumes (a few hundred thousand in the US), and distributed through a much smaller dealer ship and parts dealership. Cost goes way up because the total cost per unit is far higher.

    materials cost + labor + transportation + dealer markup + overhead(both manufacturer and distributor) /divided by a couple hundred thousand compared to being divided by Millions.

    Do the math.
     
  9. FAST FRED
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    FAST FRED Senior Member

    For a gas powered boat you need the "marine" alt , for a diesel you do not.
     
  10. powerabout
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    powerabout Senior Member

    the air is coming in the back
    the front has a centrifugal fan
    you can get sealed oil cooled if you really want spark proof
     
  11. Art1848
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    Art1848 Junior Member

    Ike,, Thanks for the Pic, Art
     
  12. keith_2500hd
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    keith_2500hd Junior Member

    there are screens on front on some models, the electrical compnents are required to be tested during manufacturing. repeated tests in propane mixture. it is not just an addition of components and charge up. ask anyone that has done a flaming somersolt into the air, was that auto part worth it.
     
  13. Ike
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    Ike Senior Member

    I have investigated numerous boat fires. On several of those the spark was the direct result of an automotive part, usually the starter but I can cite one case in which it was the alternator.

    Fire requires air, fuel and an ignition source. The Fuel, ventilation and electrical regulations are intended to eliminate one or more of those. That's why ignition protected parts such as alternators are required. That's also why marine carbs are required.

    The USCG regulations do not require ignition protection for alternators on diesel powered boats, but ABYC recommends using ignition protected alternators and onboard generators on all boats not only gas powered boats.
     
  14. missinginaction
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    missinginaction Senior Member

    Absolutely right on the use of quality marine grade parts. Safety is the most important consideration. That said, I've also found that marine grade products last longer and hold up much better in the damp marine environment.
    How do I know this? Well, in my misspent youth I did use a couple of electrical components from the local auto parts store. I was careful about fuel system maintenance and never had a problem but the auto parts failed quickly due to corrosion.

    Another aspect of this explosion proofing that I don't often see mentioned is ventilation blowers. I have two of them installed in my little boat and they run whenever the engine is running and when I'm fueling. My thinking in installing two (wired in parallel) is that should one fail I have a back up. They cost less that $100 and are cheap insurance.
     

  15. sdowney717
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    sdowney717 Senior Member

    I have rebuilt both my Delco marine alternators and they have screens on the front too.
    Makes sense though that the air is flowing in the front and out the back. I have thought too much screen means they get too hot.

    On my daughter's Jeep, I think is a Denso alternator. I replaced the brushes, The entire brush area is sealed in an interior casting metal box, which means no spark possible. It is actually a nice marine capable alternator as is.

    So some of these are perfect for marine use with no modification simply by original design.
     
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