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  1. #1

    Default 1975 70hp johnson over charging

    Giday Iím from New Zealand and my 1975 70hp Johnson is over charging up to 25 volts at the battery. I have replaced the rectifier and tested the old one and the new one both getting the same results. There is no regulator red wire runs straight to the battery wire on the starter relay. I canít find any threads on over charging that relate to the problem Iím having and our local marine guy didnít want to know because the engine is so old parts are to come by in New Zealand (fear enough) but I would like it to get me through this summer till I can afford to get another motor. Thanks in advance.

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,807

    Default Re: 1975 70hp johnson over charging

    Never heard of one charging that high.---------Check your meters.------------And check ohms on the stator too.

  3. #3

    Default Re: 1975 70hp johnson over charging

    Sounds like your battery may have seen better days.
    High internal resistance (in the battery) can cause that to happen.

  4. #4

    Default Re: 1975 70hp johnson over charging

    New battery 440 cca got a new multimeter toady. Voltage was jumping from around 0v 12v up as hi as 18.5v not consistent at all. Reading the book seams to say being unregulated it won't be.consistent and it fluctuates to charge the battery if I put a regulator in it it will bounce around 0v 12v an not charge the battery. Am I correct.

  5. #5

    Default Re: 1975 70hp johnson over charging

    http://www.boatingmag.com/converting...harging-system Mate of mine is a small engen tech and he found this

  6. #6

    Default Re: 1975 70hp johnson over charging

    CDI electronics makes a regulated rectifier for your motor. Your battery should test to 13.5 volts fully charged. Did you charge the battery before you installed it. Here is the cdi # for the regulated rectifier. 193-3408 - Regulated Rectifier Johnson Evinrude


  7. #7

    Default Re: 1975 70hp johnson over charging

    Are you making your measurements right on the posts on the battery.....or somewhere else?
    Make sure all your connections are CLEAN and TIGHT!
    Sounds very much like you have a high-resistance connection somewhere.

  8. #8
    Join Date
    Nov 2011
    Posts
    1,569

    Default Re: 1975 70hp johnson over charging

    Loose/dirty connections certainly can cause erratic voltages. And/Or rectifier burnout. If you want to control the overcharging, use the CDI regulated rectifier. I believe marineengine has them. But double check all connections first. You don't want to fry that new part.

  9. #9

    Default Re: 1975 70hp johnson over charging

    Well in the end It turns out the voltage is definitely ment to be unregulated an volatile. I put a ttr50 rectifier/regulator in AND It seamed to do the job. But the motor had been running rough and I couldn't figure out why till I found a hole getting bigger in the back of the crank casing. So I'm cutting my losses and getting something newer and service able.

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