converting 12v diesel to 24v

Discussion in 'Diesel Engines' started by Lady Sophie, Jun 17, 2016.

  1. Lady Sophie
    Joined: Aug 2007
    Posts: 13
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    Location: Lake Erie

    Lady Sophie Junior Member

    I am building a 33' heavy displacement cutter rigged sailboat for long ocean passagemaking. I have a Universal M35 diesel which is a 12v system. Can I convert to a 24v system? If I replace the 12v alternator with 24v do I need to convert the engine components (starter obviously, instrument panel)? An option would be to install a dedicated 12v battery and charge from the 24 volt system? How would the instrument panel interface? Any suggestions? Keeping the 12v system is not an option. Windlass, autopilot, refrigeration, watermaker, radar, pumps, lighting are all 24v. I anticipate a late summer launch. Thanks,
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    It will be cheaper and easier to change the starter to 24V. Are the gauges electrical? For example, fuel , oil pressure and temperature. They use very little power, and you could keep them at 12V by using a simple resistor voltage divider.
     
  3. Lady Sophie
    Joined: Aug 2007
    Posts: 13
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    Location: Lake Erie

    Lady Sophie Junior Member

    Gonzo, Thanks for the response. Yes, the sensors - including glow plugs - and instrument panel are all 12v. I am a retired mechanical engineer but stupid when it comes to electrical problems. I am considering running both 12v and 24v alternators but am concerned about HP draw - and room in the engine space. That would give me a completely independent redundant engine system which is not a bad idea on the ocean. Do you have suppliers/website recommendations that I should investigate for specific components?
     
  4. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    " I am considering running both 12v and 24v alternators but am concerned about HP draw"

    Your 24 volt conversion will not be hard. You will need the 24V starter.

    Remember tho the same amps alt. in 24V will require 2 x the hp of the 12v unit.

    I would see if dual belts could be fitted to take the higher load.

    Sensors take very little juice , and glow plugs operate a short time.

    I would use a center tap, of the 24v batts (the electrical engineers wont like it) but the few amps of 12v required to operate a few gauges is too minor to contemplate.

    A Big truck 24V alt 135A should be about $140 at your local Detroit dealer. It will have a "large" frame so may need mount brackets. They are made for a remote V regulator so a marine 3 or 4 stage V reg will wire in , no problem.Purchase the alt cooling fan for the rotation when its installed

    To charge the house batts I would use the RV system, cheap and foolproof.

    It requires the start switch to have an ACC (Accessory) position , just like a car.

    When starting the ACC is not powered , but after start in the RUN position it is.

    A 24V solenoid joins the engine batts and the house batts while the key is in run from the ACC terminal.

    That]s it , when turning off the key switch the ACC is unpowered and the house and start batts are disconnected from each other.

    KISS
     

  5. M&M Ovenden
    Joined: Jan 2006
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    Location: Ottawa

    M&M Ovenden Senior Member

    Hi,

    Sounds like you are better off squeezing in a 2nd alternator. Having an isolated house bank / loads is nice - you *should* always have juice in the starter battery....

    We did this on our last boat - a 36' schooner with a 27HP yanmar. We could turn the 24V alternator on/off if we need the HP to the prop.

    Mark
     
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