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  1. #1

    Proper Starting Procedure for Onan MDL4 20KW

    I just purchased a new boat, 1987 63' CPMY, with an original Onan generator, MDL4. Unfortunately the seller is deceased so I have no information source from him. I'm wanting to make sure I'm starting the generator properly. The start / stop rocker switch on the generator itself appears to be the only mechanism for start up. I was expecting a preheat procedure but don't seem to find one in the operators manual. Is perhaps holding the rocker switch in the stop position a preheat?
    Attached Images
    1987 63' CPMY - Jubilee
    Tampa, FL

    All who wander are not lost.

  2. #2

    Re: Proper Starting Procedure for Onan MDL4 20KW

    No familiar with older Ohnos but the 2005 or 2009 ohnos I ve used only had a start switch that you pressed. No preheat. Since there are no preheat label I m Guessing this one doesn’t have preheat either
    Pascal
    Miami, FL
    1970 53 MY #325 Cummins 6CTAs
    2014 26' gaff rigged sloop
    2007 Sandbarhopper 13
    12' Westphal Cat boat

  3. #3

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Press and hold the start switch for 5 to 8 seconds at a time if recently (1 or 2 weeks) run.
    Follow the user guide of priming the fuel pump if this does not get you going.
    There should be a start/stop switch on the top of your power selector / breaker panel also.
    Last edited by Captain Ralph; 02-02-2023 at 11:46 PM.

  4. #4

    Re: Proper Starting Procedure for Onan MDL4 20KW

    If it’s like mine you hold the stop side of the start stop switch down . That runs the electric fuel pump and energizes the glow plugs …..Pat

  5. #5

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Is there an automated delay in the starting circuit? MY NL home generator has that- you turn the switch on, it heats the flow plugs for about 10-15 secs, and then cranks the engine.

  6. #6

    Re: Proper Starting Procedure for Onan MDL4 20KW

    I have two of them on my Bertram. On mine you hold the toggle start/stop switch to stop for about 10 sec. and then start it. If in a colder climate you may need to do it twice.

  7. #7

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Thanks! Holding the rocker switch in the stop position as recommended for a preheat seemed to do the trick. Started right up.
    1987 63' CPMY - Jubilee
    Tampa, FL

    All who wander are not lost.

  8. #8

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Quote Originally Posted by pmurphy View Post
    I just purchased a new boat, 1987 63' CPMY, with an original Onan generator, MDL4. Unfortunately the seller is deceased so I have no information source from him.
    I'm wanting to make sure I'm starting the generator properly. The start / stop rocker switch on the generator itself appears to be the only mechanism for start up. I was expecting a preheat procedure but don't seem to find one in the operators manual. Is perhaps holding the rocker switch in the stop position a preheat?
    I have the same boat. 1987 63' MY. Inside your electric panel, to the left of the wheel. On the left side at the very top, you'll see a Start/Stop toggle switch. On mine, the Onan is Generator 1, so I set the bottom rotary switches both to 1. Flip both breakers to Generator power. I deenergise all panel breakers before starting.

    1. Flip the breakers from shore to Generator
    2. Insure both bottom rotary switches are on one
    3. Turn off the panel breakers
    4. Toggle the Generator panel switch to start and hold til it starts
    5. Flip the panel breakers you need to on

  9. #9

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Quote Originally Posted by pmurphy View Post
    Thanks! Holding the rocker switch in the stop position as recommended for a preheat seemed to do the trick. Started right up.
    Sorry I typed wrong. I thought you had the ole mechanical fuel pump and heaters when you started.
    Glad you got it figured out.

  10. #10

    Re: Proper Starting Procedure for Onan MDL4 20KW

    Pat, I've had my 63 about 12 years now. If you need any help, PM me. Paul.
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