Merc 40 Question

Discussion in 'Outboard Maintenance' started by skelly, Mar 4, 2011.

  1. skelly

    skelly Well-Known Member

    My 2002 Merc 40 2-stroke is having a tough time starting if the engine is left, not running, tilted up for any time. This is a real pain as I don't like to trailer the boat with the engine straight down. If I ride to the ramp with it up, I'll have to wait a full 30 minutes before I can get her started once the engine is straight down.

    If I trim it up while running, it runs fine. But if I leave it up while fishing then try to start it, it won't start. If I leave it straight down for 10 more minutes, I can get it to start. Gas line is not pinched in the tilt position. Any ideas?
  2. Brett

    Brett > PRO STAFF <

    I was going to say an air leak is allowing the fuel system to siphon back into the tank
    but that would be solved by refilling the system with the fuel line primer bulb before starting.
    It sounds like the engine is flooding as it will fire up after letting it wait and then starting.
    If it's flooding then it's probably due to the float valve not seating properly.
    I'd be thinking about rebuilding the carburetor.

  3. skelly

    skelly Well-Known Member

    Okay, I'll check the fuel line for air leaks. Any where else? Could the engine flood from being tilted up? It does seem like it is flooding when I try to fire it up, but I attribute that to turning the key like 10 times once I realized the engine wasn't starting. So flooding seemed like a secondary problem (cause by me trying repeatedly to start it). If it does flood merely by tilting the engine up, is there a way to stop that?
  4. Brett

    Brett > PRO STAFF <

  5. mark_gardner

    mark_gardner I Love!

  6. Frank_Sebastian

    Frank_Sebastian Well-Known Member

    Do you unplug the fuel line when towing? It could be that simple, but other things to try is advance the throttle a few times before starting to load the cylinders with fuel or make sure you are pumping the primer bulb slowly and stopping as soon as it get firm. If the main jet is leaking it could be getting too much fuel and flooding.

    After that is all said you might try adding engine tuner to your fuel for a while and if the float is sticking it may just clear up the problem.

    Best regards,
  7. skelly

    skelly Well-Known Member

    Thanks for this. Just a question though, should I be disconnecting the fuel line? I've never done that with any boat I've had. Is there a logic to this?
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