Mercruiser 188/888 starting and running but no thrust

Discussion in 'Sterndrives' started by Mark TR, Nov 3, 2020.

  1. Mark TR
    Joined: Nov 2020
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    Location: Cincinnati

    Mark TR New Member

    I have a new (to me) 1972 Tom Sawyer 18' runabout with a Mercruiser 188hp/888. It starts fine, runs fine, but I have no thrust in the water. I am brand new to boating, so I am sure I am missing something obvious, but I have no idea what it is. Big case of "I don't know what I don't know". Can anyone give some pointers as to what I may be missing? Its almost like its stuck in neutral, but as far as I can tell there's no switch to change gears. Thanks for any pointers anyone can give!
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    You mean it doesn't go into gear, or it does go into gear, but lacks thrust ? We are all confused by this ! :)
     
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Try boat out of water. Put in gear. Turn off.

    Try to spin prop by hand.

    probably have a prop problem with the clutch
     
  4. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If it goes into gear, it could be a spun propeller hub, a spun coupler, a stripped couple/input shaft splines among the most usual culprits.
     
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  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It sounds like the boat owner does not know how to put it into gear, more than it goes nowhere when put into gear.
     
  6. Mark TR
    Joined: Nov 2020
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    Location: Cincinnati

    Mark TR New Member

    I move the throttle forward (Or backwards) and the engine revs up, but it doesn't move. As
    You're probably correct! Here are a few pictures of the throttle and the dash board... should it go into gear automatically?
     

    Attached Files:

  7. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you look in the engineroom, the shifter cable connects at the top where the shift switch interrupt assembly is. You should see it move when you shift. Ideally, buy a shop manual, because it will have photos and diagrams to help you locate what to look at.
     
  8. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    The control handle,slides in/out, possibly by engaging the black button in the center of the hub.
    This allows the throttle to be advanced without engaging the gears, for starting and warmup functions.
     
  9. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    The handle controls rpm, but first you have to put it into gear. I do not have the same control handle on my 1972 I/O as your mercruiser but I suspects it slides in or out, or the button in the middle of the handle controls the clutch.. On mine, which has a separate button that is pulled out or pushed in, out is neutral, in is in gear. You can access the Mercruiser Service Manual at Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years! https://boatinfo.no/lib/library.html# You need Adobe Flash Player to read the manuals. You want service manual #1 As far as I know there is no user manual for boats this old.
     
    Last edited: Nov 4, 2020
  10. Ike
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    Ike Senior Member

  11. fallguy
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    fallguy Senior Member

    If you can't figure out how to shift her, I think you need to find a boat friend to show you the ropes.
     
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  12. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Is the engine a Ford 302, 2bbl carb etc? These were fairly common back then. I have checked a few sources and parts for the engine are generally available. Some people expressed concern about getting marine exhaust manifolds. But Marine Engine Parts carries them Ford V8 302/351 CID 188, 233, 888 - MerCruiser Exhaust - Exhaust Manifolds & Risers - Exhaust & Cooling https://www.marineengineparts.com/exhaust-cooling/exhaust-manifolds-risers/mercruiser-exhaust/ford-v8-302-351-cid-188-233-888 There are lots of u-tube videos on this mercruiser. If something is wrong with the throttle control, you may be able to pick up a used one on ebay. I found one for my boat on ebay and bought if for the parts.
     
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