starting problems

Discussion in 'Gas Engines' started by themadball, Jul 7, 2012.

  1. themadball
    Joined: Jul 2012
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    themadball New Member

    I have a mercruiser 3.0 alpha... It starts great when cold but once we have run it for 30 minutes or more and shut it off it is hard to start back up? ANy ideas what is causing this?
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like those old lawn-mowers with magneto ignition that would not re-start when hot, you had to let them cool down a while. But I doubt your engine has that.
  3. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    If this was posted in the gas engine section,hundreds of people would see it.

    As it were,sounds like carb (vapour lock) problems or an electronic component in the ignition is acting up when hot.
    Perhaps someone has asked this before,try the "search' feature.
  4. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    <thread moved to the gas engine forum now>
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    These engines have no fuel return line. If it is hot under the hood fuel in the carb and pump evaporates leaving you with a classical vapor lock.

    Solutions: a blower, an extra large vent in the transom or an electric fuel pump in the tank or near to it.
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    FAST FRED Senior Member

    It is also possible that the inlet valve in the carb is leaking , which would flood the engine as the fuel pump pressure bleeds down.

    Frequently this can be smelled.


  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    It could be one of a few different things and any reasonably experienced tech can sort this out pretty quickly. Not likely what you wanted to hear, but diagnosis can be difficult without having the problem at hand. Most shops will be happy to diagnose your boat, for a fee of course, which is usually fairly easy to take (typically around 50 bucks). With the diagnose in hand, you can make the fix yourself or as they hope, just let them do it.

    Nurse maiding you through all the possible situations that could cause this isn't likely to help much (no offense intended) without considerably more information, such as what does she sound like when shutting off, does she stumble for a while then die, maybe just quits, does she drop RPM before she dies, do you smell gas when you're trying to fire it back up, can you see fuel pumping from the accelerator pump orifices, when you move the throttle linkage, is the choke wide open, etc., etc., etc. These are all simple observations, that any tech will preform during the diagnose, usually one will lead him down a path to the real problem(s). Simply put, if you don't know what to look for, how will you know when you've found anything? The best advice would be to have a mechanic look her over. 5 minutes of run time and he'll probably know what's wrong and you can change out what you need to.
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