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Amps draw per horsepower

Discussion in 'Boat Electronics' started by Peter Hendra, Mar 8, 2007.

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  1. Peter Hendra

    Peter Hendra Guest

    All this talk about circuit breakers has reminded me of something I
    have been meaning to do.

    I have a 1.5 horsepower 12 volt electric motor that powers my anchor
    winch by a worm wheel.

    Can anyone advise what the current draw is likely to be under load or
    is this not enough information?

  2. Peter Hendra

    Peter Hendra Guest

    Hi Jack,
    Thanks for this.
    No, I'm stupid. There is no fuse. I never knew what size to put on it
    and it was one of those things I always was going to do.
    This has cost me. Last year when I soloed the Atlantic as my wife and
    son were back in Australia for his schooling, I installed a switch
    from the cockpit in addition to the foredeck up and down foot
    switches. I also installed a relay at the winch end for the cockpit
    switch. As I couldn't see the lay of the chain when hauling up I made
    a "wanderlead" from switches and a cable I had on board at Arricefe in
    the Canaries as I couldn't buy anything else locally. Worked well
    except I neglected to turn the up switch off once and consequently
    burnt out the windings. I now have waterproof push switches that will
    prevent this.

    All I know is that the winch is 1.5 HP from the brochure. It has been
    a great winch for over 14 years requiring only a new set of brushes.
    Made by Sindico in New Zealand - all bronze, it was half the price of
    a Maxwell. It sold so well that Maxwell bought them out and shut them
    down. Thus, I cannot get any information.

    At the moment I am in the yard in Trinidad getting ready for the
    Pacific. I bought a chain counter in Sydney and have to go through the
    fun of drilling two holes in the bronze for the magnet and sensor.

    The winch is powered by a Chinese starter motor - at least that is
    what it looks like. Three connections, one for positive and two for
    negative up and down. would 150 AMP be OK?

    cheers and thanks
    N.Z . yacht Herodotus
  3. Jack Erbes

    Jack Erbes Guest

    1 HP = 746 Watts,
    1.5 HP = 1119 Watts,
    1119 Watts / 12 V = 93.25 Amps

    If it has a fuse on it, I wouldn't be surprised if it were quite a bit
    more (150A?) to allow for the starting load.

    This is all theoretical, of course. Is there a fuse on it?

  4. Jack Erbes

    Jack Erbes Guest

    Your wife and kid were busy so you single handed across the Atlantic?
    Sounds like you might not be the average sailor. My compliments sir!

    Anyway, don't let me talk you into anything foolish. I am an idle
    speculator and my experience with anchor windlasses is limited to having
    used a few here and there.

    Just as a matter of comparison, here is a manual for the Lewmar H2/H3
    models. I realize it might not be a direct comparison but the numbers
    seem similar to the ones we are bantering around here.

    The H3 is sized for 12-15 meter boats and 5/16" or 3/8" chain. It is
    rated at 1000 Watts, has a 860kg/12V and 970kg/24V maximum pull, and a
    45kg working load. The manual calls for it to be fused at 85A on 12V
    and 60A on 24V. So it looks like if yours is similar, starting with a
    150A fuse might be a little too high.

    I'd probably start with a 75A fuse and make sure the wiring was all
    sized right for the run lengths. And I'd agonize over the cost of it
    all and also have some 75A and 100A spares available.

    If it blew a 75A fuse I'd like to try to immediately get my eyes and
    hand on the motor housing to see how hot it had gotten before I went to
    a 100A fuse.

    Of course having things like clamp on Amp meters to watch with the motor
    under load are wonderful for learning about the limits.

    I learned the hard way once that a windlass that was properly sized for
    lifting the ground tackle was not up to the sustained pull and run of
    getting the boat up and over the anchor. Since then I've come to think
    of them as something that you should lighten the load on as much as you can.

    Good luck with that and the rest of your trip.

  5. Peter Hendra

    Peter Hendra Guest

    Hi Jack,
    Thanks again for the information. I shall do as you suggest and work
    up to progressively bigger fuses. This approach makes much sense and
    actually makes me feel a little stupid for not thinking of it as my
    role is a technical project manager(telecommunications) but sometimes
    you can't see the wood for the trees.

    As to the Atlantic crossing, thanks but I don't really deserve the
    compliment as I really had no choice. As a family we had sailed to
    Spain via the Red Sea from New Zealand. To be perfectly honest, apart
    from bad head-on weather north of the Canaries where I lay for a day
    to a sea anchor, the trip was probably the best long term sailing I
    have ever done - days under genoa alone with the seas and wind on the
    starboard quarter. The hardest part was to take a deep breath and get
    started, as well as the loneliness and the lack of sleep. I made up a
    digital counter attached to a piezo alarm that would go off after 20
    minutes (or whatever I set - each count was one second) if I didn't
    push the reset button. I did worry beforehand however that I might go
    crazy from the isolation but after a while it became a spiritual,
    peaceful journey that was rather sad to end once I ended up in

    Incidentally, getting a parachute sea ancor back on board is a lot
    harder by one's self as one simply cannot motor up to it whilst
    another person pulls in the rode. In future I may not attach the trip
    line and thus will not have to worry about fouling it with the prop.

    cheers and again, many thanks

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