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  1. #1
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    Red face no spark Mercruiser 140Hp 3.0L

    Hi. I have 140 HP 3.0L Mercruiser and I only get spark when I run a wire from positive terminal of coil to a positive wire somewhere on engine e.g starter motor or solenoid. Motor starts fine then, and I undo wire and all is Ok till I next need to start. I am sure it is something simple but can't work it out.
    Any sugeestions? Thanks.

  2. #2
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Do you have a lanyard switch somewhere at the helm?

  3. #3
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    Default Re: no spark Mercruiser 140Hp 3.0L

    disconnect the battery, and clean the connections on the starter. I had the same problem and with a switch on the dash,wired to the pos side of the coil i just flip the switch start the boat with the key and when i want to shut off the motor i turn off the key and it will still run till i flip the switch.

    Very important if your running points the switch stays off till you start the motor. Or if the points are closed and the switch stays on you could fuse the points.

    Planes are wired this way, old cars and some racing boats.

    Nothing i did fixed it. I believe i need a new harness nla anywhere.

    I have a 86' 140.

  4. #4
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Negative.

  5. #5
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Thanks for that. I will set something up in the long run. My wring is a bit of a mess so new harness may be worth it. Where did you run the other end of wire to? Cheers.

  6. #6
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    Default Re: no spark Mercruiser 140Hp 3.0L

    i followed the pos cable and the first connection i added the wire. I used a brass end, and shrink wrapped it.

    I ran 2 wires together, purple to a unused flip switch at the helm marked it ign. Made it the first on the left. Really all it took was i think less then 15 feet of wire. And then i tied it to the wires under the gunrail.

    I swear if it took 15 minutes.

    I got to ask you don;t have a kill switch if yes bypass it, that there could be your problem.

    Also your keyswitch is good.

    I have a friend who took out his keyswitch, got a momentary switch there with a hotwire to the coil on a flip switch just like i have.
    Last edited by chiefalen; 03-11-2011 at 09:22 PM.

  7. #7
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    Default Re: no spark Mercruiser 140Hp 3.0L

    i see where you replied to the kill switch.

  8. #8
    Join Date
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    Northboro, Ma, USA
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    Default Re: no spark Mercruiser 140Hp 3.0L

    First thing to do is to purchase a 12 volt test light. Usually found at a automotive store.

    This is my understanding of your issue, tell me if I am wrong.

    When you go to start the engine with the key switch it will crank over but NOT start, correct?
    When you connect a 12 volt source to the coil from some where else it starts and runs until you turn it off with the key, correct?
    when you try to restart it only cranks over but will not fire (start) again, correct?

    On your starter you have a solenoid, on the solenoid how many connections are there? one large and two small? and when I ask how many connection I mean connections with wires!!!

    If you have two small connections (wires) then what happens is, when you crank over the motor power is transfered at the solenoid from the large connection to one of the small connections (during the cranking only) and this supplies power to the coil, again only when cranking.

    Two issues that will not allow this to happen,
    1. the solenoid is bad (internals of the solenoid are corroded).
    2. The shift interuptor switch is engaged or bad and shorting the 12 volts to the coil to ground. (make sure you are in nuetral and check interuptor switch function). if you do not know what the shift interuptor switch is or does just ask.

  9. #9
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Does this engine have electronic Iignition or Ignition Points and condenser?

  10. #10
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    Default Re: no spark Mercruiser 140Hp 3.0L

    1986/7 would be points unless it was converted to electronic.

  11. #11
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    Default Re: no spark Mercruiser 140Hp 3.0L

    I don't see where the original poster listed the year.

  12. #12
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    Default Re: no spark Mercruiser 140Hp 3.0L

    He started another thread and he posted it there, the carb thread about a reuse of the base gasket and a vacuum leak.

  13. #13
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Sounds like a bad ballast resistor.

  14. #14
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    Default Re: no spark Mercruiser 140Hp 3.0L

    in his case it would be a resistor wire.

  15. #15
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    Default Re: no spark Mercruiser 140Hp 3.0L

    If the original wiring harness is in place and the ballast is bad, the engine would start and run until the key is released from the start position and then it would stall. The second small post on the starter solenoid delivers full battery voltage to the ignition system while the starter is engaged.

  16. #16
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Yes I agree and made mention of the same in previous post

  17. #17
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    Default Re: no spark Mercruiser 140Hp 3.0L

    I have owned two 140HP 3.0 Mercruisers. Both had ceramic ballast resistors.

  18. #18
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    Default Re: no spark Mercruiser 140Hp 3.0L

    I worked on Mercruiser's for 15 + years, From what I remember 1980's thru early 90's until they finally went to electronic (dont remember the exact year) I never saw a ballast on a mercruiser 4 cyclinder or 8 cylinders when they had points prior to the thunderbolt ignition, They used the GM style resistor wire,
    My feeling is if it had a ballast it may have been added due to a bad wire or suspected bad wire or connection. They may have used some prior to the '80's but again i dont remember actually seeing any.....OMC and other marine motor manufactures did use them even on V8's especially ford motors.

    I used to have 3-4 one gallon bags with points, rotors, and condensors each season when doing spring tune ups for customers......Not that I have seen all but sure seen many.

  19. #19
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    Default Re: no spark Mercruiser 140Hp 3.0L

    do a compression and vacuum test ghost.

    Just kidding.

    My 2.5 omc 86'and my 86' merc 140 has a resistor wire.

    Just saying i have the boat in the backyard.

    Before running the hot wire i stated to clean the starter connections.

    I in essence i made a new harness, when i got the boat it sat for 8 years.

  20. #20
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    Mar 2011
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Hi kghost. yes you have issue correctly understood. Have 2 small and one large wire on solenoid. The solenoid does look ordinary. There is a crack in the plastic casing. I think that may be the issue. Will play around as see what happens. Will also check shift interruptor switch. Where will I find that? Thanks heaps, Anthony. PS does anyone know how I change my mis-spelt name?! I couldn't do it in My Profile? PPS I lived on east coast for year with then wife - Block Island, then 6 months driving around the country in a piece of crap Jeep. Great adventure! Amazing countryside.

  21. #21
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    Default Re: no spark Mercruiser 140Hp 3.0L

    See where the shift converter is there is a micro switch sits in a v notch. When the converter moves the switch is activated you have to see if the button pops back out. Or you can simply unplug it and try to start the motor with it unplugged.

    I should not actually activate unless the prop is in the water and there is a load. I simplified the explaination.

    You say the slav solenoid has a crack? Or the one on the starter ?

    See you say it cranks and starts without jumping the slav, with a wire to the coil pos side.

    Whats the story with this boat a litlle detail you just got it ?

    Maybe it sat a long time ?

    Did it start right and then the problem just popped up ?

    Remember i posted i had the same problem, well i willing to bet your gona wind up after 2 weeks doing what i first posted.

    I keep my boat on a trailer at my home and to tell you the truth 15 seconds i could jump your boat if i wanted to steal it with a keyswitch.

    While we are talking about the keyswitch you did look at the back of it ?

    I tell ya a lawnmower switch could be used.

    A bad keyswitch could also be the problem.
    Last edited by chiefalen; 03-12-2011 at 11:14 PM.

  22. #22
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Thankyou chiefalan. No forgot to check keyswitch but it does turn over every time. Will check though. Starter solenoid has a crack in the plastic housing at end of solenoid. Problem started after sitting for a while. I am confident with all the info I have received I will solve the problem. And I would be more than happy if the end solution is simply the toggle switch to give current to the coil on starting. 'Ooroo. (goodbye in Australian!)

  23. #23
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    Default Re: no spark Mercruiser 140Hp 3.0L

    Replace the starter with a marine replacement or remove it and bring it to a repair shop with the understanding it is MARINE NOT automotive!!!!

    I would tell you just to replace the solenoid BUT there are certain things that make a marine starter different than a automotive and these things MUST REMAIN the SAME!!!

    The cracked plastic cover is most likely your issue. The small terminal that should have a PURPLE wire on it is not getting the 12 volts needed when cranking.. This purple wire is ONLY used during the cranking over of the engine when starting and supplies the 12 volts to the coil at that time ONLY, once you release the key to the RUN position the 12 volts comes thru the key switch thru wire harness thru the resistor wire to the coil.

    Hope this makes sense and corrects your problem!!!

    The slave solenoid does not supply 12 volts to the coil and is only a "slave" to the starter solenoid for yellow with red wire that energizes the starter solenoid (the other small terminal)

    The starter solenoid should have two small terminals I and S, I equals ignition (puple wire) S equals start (crank) (yellow with red stripe wire)

    Not sure your interuptor switch is a issue at this time. Get the boat to start correctly first and then if you have a "shift out of gear" problem when in the water we can go back to the interupter switch

  24. #24
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    Default Re: no spark Mercruiser 140Hp 3.0L

    If it starts and runs after the jumper wire to the coil is removed, it's not the shift interrupt switch.

  25. #25
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    Default Re: no spark Mercruiser 140Hp 3.0L

    You have a pm

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