Mercury Blue Band issues

Discussion in 'Outboards' started by Amir, Dec 22, 2020.

  1. Amir
    Joined: Dec 2020
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    Location: Australia

    Amir Junior Member

    Hi all,

    I'm new to boating and boats. I recently bought a half cabin with mercury outboard 50hp 4 cylinder 2 stroke.
    The issue I have is that the starter gear (which I recently replaced) works and engases the flywheel. But the flywheel doesn't like to spin.
    I tried to turn it by hand or even socket. But no luck.

    Should I be able to turn the flywheel (with plugs out) by hand? If yes what direction?
    Appreciate in advance if anyone knows what the issue is. I attache some pics of the motor.

    Thanks again
     

    Attached Files:

  2. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Check all electrical connections and battery condition first.
    If it won’t turn by hand, it may be seized from water intrusion or lack of lube oil in the fuel.
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    It very much sounds like it is seized. But take those plugs out, and look for signs of rust.
     
  4. Amir
    Joined: Dec 2020
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    Location: Australia

    Amir Junior Member

    T
    hanks for the reply. Is it a good idea to disassemble the crank case or replace it with a power head sold on ebay?
     
  5. Amir
    Joined: Dec 2020
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    Location: Australia

    Amir Junior Member

    I cannot actually see rust through the little hole on plugs. I was thinking to take all apart but not sure if that is a good idea as I could not find the assembly manual to put them back on.
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    What about the plugs themselves, are any rusted at the electrode end ? There are a number of ways water can get in, but usually it is big trouble, what do you know of the history of it ?
     
  7. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    That is an old motor that I would think not worth spending money and time on, but it doesn't hurt to diagnose what has happened to it.
     
  8. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    While you are at it, with the motor in neutral, see if the propeller will move, unlikely to be the problem area, but try it.
     
  9. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    That engine doesn't look to be in bad shape on the outside anyway. When I was young we used to fix up old cars. On more than one occasion we came across an engine that had the rings rusted a bit and stuck to the cylinder walls. We removed the plugs and placed some lightweight oil into the cylinders. If I remember it right a friend of mine was partial to automatic transmission fluid due to it's high detergent properties. I'd guess you could use any light oil. Let the engine sit for a day and see if you can break it loose with a breaker bar and socket. Don't go crazy with it. At first be gentle and try to work the flywheel back and forth to break things loose. If you have access to an air compressor you could use a air gun to try to shock the engine loose. Again be gentle. When I'm rotating tires I run the compressor at 90 PSI to get the wheel lugs off. If I were trying to break that engine loose I'd dial the compressor down to maybe 40 or 50 psi. That way the air gun would be gently shaking the crank piston assembly. Try it by hand first though.

    If that doesn't work you likely have bigger problems.
     
  10. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The engine is definitely seized. You can try several things to force it to turn. However, all of them are likely to cause further damage. For example, if a bearing is seized and you force it to turn, it will damage the block and won't be rebuildable. The best thing to do is to disassemble the engine and see what is wrong.
     

  11. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Every chance salt water has got in, a common points of entry are leaking head gaskets, water jackets that have perforated through corrosion (highly likely with an older Mercury) or the engine may have just overheated and seized as a result. In the latter case it would be more repairable, but salt water intrusion that has not been immediately acted upon, is likely to have wrecked the steel internals, the main one being the crankshaft.
     
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