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  1. #1
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    Default Risk of not using a 90 amp starter solanoid fuse

    Hi all.

    motor is a 2003 mercruiser 350 mag mpi.

    My 90 amp starter solanoid fuse has gone and i was looking at an official replacement part and the cost is around $70-90 in australia for the official fuse which is hefty price tag for a fuse. I was wondering what risk i might be taking if i do not run the boat with this fuse ?

    There is a circuit breaker in the ignition line so was thinking it may not cause too much of an issue if i dont replace the fuse. Plenty of motors do not have this fuse. Otherwise might make up a non official 90amp fuse cause it will only cost about $10

    Thanks

  2. #2
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    it`s nothing special, was being called a "lawer fuse" but most older boats never had one.Plus you already have a 50A CB in that line.
    NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

  3. #3
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Ok. I think i will just not bother replacing it. The cost is too expensive for the genuine part.

  4. #4
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Bt Doctur View Post
    it`s nothing special, was being called a "lawer fuse" .
    That's Bond-o's term for it.

    Just remember to disconnect the battery before you work around the starter. No doubt you shorted it out with a wrench when working on the engine, just imagine what would have happened if it wasn't there. That 50A breaker wouldn't have protected anything.
    Don S.


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  5. #5
    Moderator Bondo's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by shankos View Post
    Ok. I think i will just not bother replacing it. The cost is too expensive for the genuine part.
    Ayuh,.... It seems that the Lawyer Fuse was added 'bout the time 'puters were added into the engine management systems....
    To All their motors, 'puter efi, or not..

    My motor ain't got a 'puter, 'n I didn't put in the Lawyer Fuse either...
    Any Grease is Better,..... Than No Grease at All.......

  6. #6
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Don S View Post
    No doubt you shorted it out with a wrench when working on the engine, just imagine what would have happened if it wasn't there. That 50A breaker wouldn't have protected anything.
    I was asking what risk i run without the lawyer fuse being in the circuit and a mistake happens ? What exaclty might i imagine could happen ? I had thought the circuit breaker would be sufficient.

  7. #7
    Rear Admiral Fishermark's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Without the "lawyer fuse" there is no protection for the main battery cable. If you short that out without disconnecting the battery first... sparks will fly and something will melt or burn. That's why you always want to disconnect the battery whenever working around the starter.

  8. #8
    Moderator achris's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Fishermark View Post
    .. That's why you always want to disconnect the battery whenever working around the starter.
    Nah, it's more fun 'live'....

  9. #9
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    except it has nothinbg to do with a battery cable. thge 90A connection is what supplies power to the 50A breaker, then thru the harness to the dash.
    NO PERSONAL QUESTIONS, THIS IS WHAT THE FORUM IS FOR.

  10. #10
    Rear Admiral Fishermark's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    I actually learned that the hard way - working on my 56 Chevy years ago I was lazy and didn't want to disconnect the battery. I was using a box end wrench on the starter solenoid and touched the other end of the wrench to the metal brake line.... of course then ended up disconnecting the battery AND replacing the metal brake line. At least it wasn't the fuel line.

  11. #11
    Rear Admiral Fishermark's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Bt Doctur View Post
    except it has nothinbg to do with a battery cable. thge 90A connection is what supplies power to the 50A breaker, then thru the harness to the dash.
    Fair enough... that's true. I guess the point is to always disconnect the battery when working around the starter

  12. #12
    Moderator Bondo's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Fishermark View Post
    Fair enough... that's true. I guess the point is to always disconnect the battery when working around the starter
    Ayuh,... The Lawyers have done all they can to save the stupid, from themselves....
    That's why step-ladders weigh Twice what they should, with All the safety stickers all over 'em....

    Common Sense, still rules,... disconnect the battery....
    Any Grease is Better,..... Than No Grease at All.......

  13. #13
    Moderator achris's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by Bond-o View Post
    Ayuh,... The Lawyers have done all they can to save the stupid, from themselves........
    I say "let Darwin take control"...

  14. #14
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Does a 90A fuse blow all by itself? No, Therefore, the fuse did it's job. Obviously, the battery was not disconnected and it prevented further damage.
    Had it not been there, we might be reading a thread of the battery blowing up, or the battery terminals melting off, or whatever. Without that fuse, that wire would have been hooded to the starter directly, and very well could have melted the battery cable. Depending on where it was shorted.
    That fuse is there for the un-trained backyard DIYer. Not the Mercruiser certified tech.
    Don S.


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  15. #15
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Always disconnect the GROUND cable first!!!!! Or you'll be sorrrrry!!
    Terry
    87, 4WINNS H 190
    470/Alpha I

  16. #16
    Moderator achris's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by stonyloam View Post
    Always disconnect the GROUND cable first!!!!! Or you'll be sorrrrry!!
    Oh, and why is that???

  17. #17
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Because if you are unbolting the positive (from the battery or starter) with the ground still attached and the wrench touches grounded metal you will get lots of sparks and a very hot piece of steel in your hand. If cable had been removed from the battery negative, nothing would happen.
    Terry
    87, 4WINNS H 190
    470/Alpha I

  18. #18
    Moderator achris's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    I like that answer... ... But it's a little too 'safe' for me

    If you're not living life on the edge, you're wasting space....

  19. #19
    Moderator Bondo's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Quote Originally Posted by achris View Post
    I like that answer... ... But it's a little too 'safe' for me

    If you're not living life on the edge, you're wasting space....
    Ayuh,.... I think, That's why I like you,....
    Any Grease is Better,..... Than No Grease at All.......

  20. #20
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    That's almost as much fun as checking the 120v AC breaker panel with the shore power cable connected and live! A few years ago, while waxing our boat before its splash, I heard a scream and cursing from a nearby, docked boat. The marine mechanic's "assistant" was checking and tightening the screws on the AC circuit breakers without disconnecting the shore power cable. Dumb!!! Hy

  21. #21
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Since I am being Safety Sam here: If you are ever working on a live circuit (or one that MAY be live) keep one hand in your pocket, so that if you do touch a live wire the current will go down through your feet (and knock you on your butt) rather than across your chest to the other arm (and KILL you).
    Terry
    87, 4WINNS H 190
    470/Alpha I

  22. #22
    Moderator achris's Avatar
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    Default Re: Risk of not using a 90 amp starter solanoid fuse

    Now, if you really want some fun... Don't try this at home!!! Was troubleshooting a 3-ph pump not working one night... (Years ago on the back deck of a workboat in the Philippines)... was probing around, with my finger and found that there was 440vac where there shouldn't have been... I think I was buzzing for a couple of hours after that one...
    The world takes on a whole new perspective when viewed from 100' below...



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    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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