1983 mercruiser 260 350cid Low RPM issue

Discussion in 'Gas Engines' started by gatesjeff33, Jun 11, 2012.

  1. gatesjeff33
    Joined: Jun 2012
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    Location: minneapolis, mn

    gatesjeff33 Junior Member

    I have a 1983 mercruiser 260 that has been rebuilt a couple of times. On the last rebuild, the mechanic said that he couldn't get a lot of RPMs out of it. Currently it tops out at 3,000 RPMs. Brand new, the motor did 4,600-4,800 rpms.

    Is this common? or did they really screw something up? Low compression?

    Is there anyway to restore the high RPMs?
     
  2. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    the advance has seized in the distributor

    the secondarys in the carb are not working

    rebuilt a couple of times....what was diagnosed
    Does it have all original components?
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    A rebuilt motor should get the same RPMs as a new one, once it's broken in a bit. The mechanic should not have charged you for a rebuild if he can't make it work properly.
     
  4. Frosty

    Frosty Previous Member

    Was it rebuilt because of low RPM? Certainly the secondaries would be a good bet.
     
  5. gatesjeff33
    Joined: Jun 2012
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    gatesjeff33 Junior Member

    The last rebuild was... if I recall right... from a valve hitting the piston.

    If the secondary's are not working, is that generally a replacement or can I clean out the carb to get them working again? I'm new to carbs. I've cleaned them before, but they were smaller and simpler designs than the boats carb.

    Should the mechanic have retimed the advance when the engine was rebuilt? I'd assume that he would have done that, but you never know. We got the rebuild done for cheap because we are very close friends with the marina owner. I'd say it is safe to assume that it still has original ancillary components.

    Thanks for your responses. I am looking forward to getting to know marine engines better. I've already learned a boat load:)
     
  6. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    Does it still have the original Rochester Quadrajet carb?
    If so you will need someone to show you how to pull that apart or buy a book
    post a photo
     
  7. gatesjeff33
    Joined: Jun 2012
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    Location: minneapolis, mn

    gatesjeff33 Junior Member

    I'll check.... might take a day or two to get out there. I'm guessing it is still the original.
     
  8. slow fred
    Joined: Feb 2011
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    Location: florida

    slow fred Junior Member

    Was the engine running ok before the valve and piston deal?
     
  9. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If your mechanic noticed "he couldn't get any RPM's out of it" then he darn well knew what was wrong and that it was probably his fault. He screwed up, it happens, but you don't have to pay for it. If he doesn't make it right, then small claims court will quickly clear up the mess. He also knows this, so call him and get the real story or make him pay to have it done right thins time (which is what the court will force him to do).
     
  10. gatesjeff33
    Joined: Jun 2012
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    gatesjeff33 Junior Member

    I can't recall at this time. It got rebuilt 4 years ago.
     
  11. Frosty

    Frosty Previous Member

    The boat wasnt in the marina was it. Im thinking fouled prop.
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If it was a fouled prop, the mechanic would have been able to rev it up out of gear, but that's not what he said. If he had something other than himself to blame, you can bet he would have.
     
  13. gatesjeff33
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    gatesjeff33 Junior Member

    The prop is fine. It runs the same with an old prop or a new prop.

    Is low engine compression a possibility?

    The boat starts easy and runs smooth, it just can't get the RPMs up past 3k
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Nope, even with low compression (which you shouldn't have after a rebuild) the engine should pull a full set of RPM's. It's likely he reused some parts that should have been replaced and is making excuses for it. It could be as simple a distributor advance spring or a stuck weight.
     

  15. Frosty

    Frosty Previous Member

    Agreed.
     
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