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Mercruiser - Starter Cranking Slow

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  • Mercruiser - Starter Cranking Slow

    What I have done so far.
    Battery Tested good at shop.
    Cleaned all connections-
    Did voltage drop test 1.514v at Ground , .543v at Positive. ( I know they're high, read on )
    Voltage at battery when cranking 10.6v , voltage at starter 10.45v

    I'm starting to think the starter is causing the voltage drop that i'm getting because it is so excessive. I pulled the starter apart last night and with the 4 brushes against the commutator it is pretty hard to turn by hand. I'm guessing that this is an issue. If I release the springs on the brushes it spin freely.

    So is it my starter/worn brushes causing these voltage drops ?

  • #2
    Re: Mercruiser - Starter Cranking Slow

    i know how to do a voltage drop test... so why don't you tell us how your doing it? and what your using for a meter. If your doing it the correct way then you'll know exactly how much each wire is eating and how much the starter is eating. Just because you cleaned the connections doesn't mean they are any good. and you verify that with the test. you may just have bad battery cables. they go bad all the time in boats. even if it "looks" good on the outside i've just open battery cables (right down the middle) to show customers and you can clearly see all the rot and corrosion.
    just because you found it that way does not mean it is supposed to be that way.


    • #3
      Re: Mercruiser - Starter Cranking Slow

      I'm using a digital auto ranging multi-meter. To test the + voltage drop i go from the + battery post to the + post on the starter. For - i go from the -battery post to the case of the starter ( after removing some paint ). Meter set to DC volts. Is this all correct ?

      I'm still curious if the brushes should cause the amount of friction that I noticed.

      On another note - I have a dual battery setup using a Perko switch. On one battery cranking is very slow ( either battery it doesn't matter ) but on both batteries cranking is normal and I have no issues.


      • #4
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        Re: Mercruiser - Starter Cranking Slow

        Starter was the problem. I replaced it this morning and now it cranks like a banshee again.