help 1985 7.5 mercury outboard

Discussion in 'Outboards' started by kenrahe, Jul 20, 2010.

  1. kenrahe
    Joined: Apr 2010
    Posts: 101
    Likes: 1, Points: 0, Legacy Rep: 24
    Location: pomfret ct

    kenrahe Sunseeker

    guess i didn't get a great deal after all got a 1985 7.5 mercury and it runs but when i try to go full throttle it goes for a minute great then dies and takes awhile to get started again what should i look at first
     
    Last edited: Jul 20, 2010
  2. tom28571
    Joined: Dec 2001
    Posts: 2,474
    Likes: 116, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Probably a fuel issue. Loose valve in the fuel line pump, problem with vent suction in the tank, bad fuel line, fuel connector at tank or motor or clogged pickup in the tank. Something like that. Borrow someone else's tank and hose if you can to see if the problem is any of these.

    Then there is the problem of ethanol or some other mess clogging the carburetor or deteriorating a fuel line on the motor. That is the cause of most of my problems lately.
     
  3. kenJ
    Joined: Jul 2005
    Posts: 349
    Likes: 5, Points: 0, Legacy Rep: 56
    Location: Williamsburg, VA

    kenJ Senior Member

    As Tom said, if it has an external tank check the where the hose connects to the engine. All it takes is a slight leak and the engine will suck air. You said you got a deal.....suggests that the motor has been sitting for a while. Carb kits are cheap, give the carb a good cleaning and rebuild. The ports/jets are small, doesn't take much to plug them up.
     
  4. Wynand N
    Joined: Oct 2004
    Posts: 1,260
    Likes: 148, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    had this type of failure with a similar HP Suzuki engine. Turned out the spark plugs run to hot....
    Check that you have the correct rated plugs installed.
     
  5. kenrahe
    Joined: Apr 2010
    Posts: 101
    Likes: 1, Points: 0, Legacy Rep: 24
    Location: pomfret ct

    kenrahe Sunseeker

    bought new tank, new bulb an line haven,t tried changing the plugs yet it has those weird plugs that have no gap thinking of going back to a gap plug.but want to know if there is any way to test the fuel pump.it ran great in the barrel but like i said under a load it dies in a short time.
     
  6. Wynand N
    Joined: Oct 2004
    Posts: 1,260
    Likes: 148, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Sound like it can be an overheating problem since she cuts out after awhile under load. Usually starts again after cooling down a bit. See if it pisses water at the pee hole.

    To check fuel pump - prime carburetor with the hand bulb - disconnect petrol pipe from pump to carburetor at the carburetor and slip into bottle. Start motor and the pipe should pee petrol into the bottle.

    Hope this helps.
     

  7. kenrahe
    Joined: Apr 2010
    Posts: 101
    Likes: 1, Points: 0, Legacy Rep: 24
    Location: pomfret ct

    kenrahe Sunseeker

    fuel pump is on side of carb only one line to pump could there be any kind of vacum line missig or not attached that i can't see
     
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