black smoke bogs down

Discussion in 'Gas Engines' started by mark_fitzy, Aug 3, 2009.

  1. mark_fitzy
    Joined: Mar 2009
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    Location: Australia

    mark_fitzy Junior Member

    Just lately I have noticed that when I start the 15 hours old v6 Mecruiser engine alot of black smoke comes out, I rev it about 30 seconds and it dissapears. When I start to go at slow speed there is no problem, if I try and accellerate it bogs down the more I increase the throttle, If I continue to push the throttle down it hesitates, bogs down and then after a while it takes off,planes, cruises just great and I dont have a problem all day.

    I am thinking that this could be the automatic choke staying on to long or does it need a carby cleaner. Can anyone confirm this or have any other ideas.

    If it is the choke, how do I adjust it?
  2. mark775

    mark775 Guest

    Did you steal this engine?
    If not, somewhere between not bothering to call for warranty service and "Mercruisers are CRAP, I hate them with a passion, the non-OEM filters are CRAP and when I spend tons of crappy US dollars on them (not to use - just to cut open) I get mad. They suck really, really, super hard, They are just crappy Toyotas with crappy black paint, I think I'm gonna have to sue the crap out of them..." might be a logical response.
    If you stole it, well...crap. (RE: "Yanmar are crap" thread. Why doesn't anyone just call their dealer?)
  3. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Feeling a tad bitter today, 775?

    MarkFitzy, I take it you're talking about the 4.3L V6. Which version of it do you have? There's a multi-port injection version, a conventional carb version (not being sold as new anymore, but still popular on the rebuild circuit) and a new carb version with Merc's TKS automatic prime/choke feature.

    In any case, at 15 hours old it is most likely your dealer's problem, not yours- an engine that isn't even fully broken in yet must surely be under warranty.
  4. mark_fitzy
    Joined: Mar 2009
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    Location: Australia

    mark_fitzy Junior Member

    marshmat thanks for a positive reply,
    its a 1995 Regal Bowrider with a "sorry:eek: ". a new Reco Chev 262 4.3lt V6 Mercruiser style unleaded long motor, comes with new exhausts and risers, new water pump, reco balancer, new alternator, new thermostat housing, new starter, reco carberettor, new intake manifold, new electronic distributor and leads, new flywheel, marine head gaskets, new flame arrestor
    It was purchased through an insurance company off an engine importer and a mechanic installed it (three partys involved,) for the minor problem its causing its to much of a hassle to take it back to the mechanic, and fight with him and the insurance company etc

    The engine is going really well, its just when I first start the boat, after she clears out I cannot fault her. I spoke to the previous owner of the boat and he said he never had the Automatic choke on the old engine connected,
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Black smoke suggest water is burning.
  6. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    It sounds like a charge of gas is entering the manifold before it starts.
    Just take it to someone who would knows that carburator. Maybe it's a float valve problem.
  7. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    Black smoke generally indicates an over rich condition. This can be caused on start up by a carburetor that is dumping fuel (there may be a leak somewhere inside the carburetor itself that is causing your carb to allow raw fuel to drip into the intake manifold after you shut the engine down. This wouldn't cause an issue when the engine is warmed up, but you would notice it much more on a cold atart (and you do based on your post!).

    The bogging on acceleration points to an accelerator pump / power valve issue.

    Just because the carburetor is new doesn't mean that it cannot have issues. Rebuilt carbs often do. Doesn't sound like a huge issue but all in the carb.

    Good Luck,

  8. mark775

    mark775 Guest

    1 person likes this.
  9. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    I think you may have two problems. One has to do with an over-rich starting situation, the other an over-lean main jet. Both carburator issues. The second problem, hesitation, is classic fuel starvation tracable to the accellerator pump or the main jet adjustment. This is a screw adjustment.
    Both problems could also be tracable to dirty fuel. One particle could hold the float valve slightly open causing flooding when the engine sits. Another similar particle could partially close off a passageway from carb to venturi.
    The engine and carburator may have been rebuilt, but the fuel line may not have been cleaned or replaced. Make sure there's a filter in the gas line too. Make sure the fuel is brand new and not left over from last year.

  10. Frosty

    Frosty Previous Member

    When the engine is cold the choke should be shutting the venturi, but only positively, not hard.

    It should be easy to push it open with the finger but not loose.
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