Engine Problems

Discussion in 'Powerboats' started by mikealston2428, Jun 16, 2012.

  1. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    Hi All,

    I have a 350 chevy smallblock boat inboard, last trip out it started blowing black smoke and black soot.

    Any ideas on why this has happened ?

    I am going to set the ignition timing and see if this helps.

    I think this should be set to 4 degress before top dead centre, is this correct ?

    Cheers,
    Mike
     
  2. slow fred
    Joined: Feb 2011
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    Location: florida

    slow fred Junior Member

    Too much fuel. Choke stuck closed or carb id flooding. Timing doesn't change unless the distributor is loose.
     
  3. Frosty

    Frosty Previous Member

    4-6 degrees is near enough --black smoke soot is a very rich mixture. Only the choke could do this if it didnt do it last time. Or fuel bowl needle failure as above.

    Common item to stick and not work WD 40 and some waggling for 5 minutes will do it,--if you know where it is.
     
  4. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    Hi Frosty,

    Is that 4 - 6 before or after center ?

    Common item to stick and not work WD 40 and some waggling for 5 minutes will do it,--if you know where it is.

    Where is this located ?

    Thanks,
    Mike
     
  5. Frosty

    Frosty Previous Member

    Static ign timing will be 4-6 degrees Before Top Dead Center.--- BTDC

    Its not critical as when the engine running it will change to as much as 28BTDC.

    Its just a base line starting point.

    The choke is a big flap at the carburetor intake that closes when the engine is cold, increases depression pulling in more fuel for cold starts . When it warms the flap should open by a thermostatically controlled bi metal spring on the choke flap shaft.

    Google it,--Im sure there will be help for this.
     
  6. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    If the choke is stuck, is there a cable or some where on the motor to lube and free it up ?

    Thanks,
    Mike
     
  7. Frosty

    Frosty Previous Member

    A chevy350 will have an automatic choke.

    This might be a little above your skills and you may adjust something you should not but is a tiny job for a mechanic.
     
  8. mikealston2428
    Joined: Jul 2011
    Posts: 188
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    Location: aussie

    mikealston2428 Senior Member

    Hi Frosty,

    Great help thanks.

    Can you please explain - Static ign timing

    I will warm up egine drop revs to 500rpm, remove advance line at set timing

    to 4 - 6 BTDC.
     
  9. Frosty

    Frosty Previous Member

    Static means still. You turn the engine by hand until 4 degrees reads on the crank vernier.

    The points should be breaking open. If your electronic ign static is not optional you will need a stroboscope to look at the same vernier on the crank pulley but now your doing it with engine at idle or a particular RPM as per the manual.

    However I can guess that 4 degrees will be at idle ( what ever the manual says that is 500 RPM) set that first although may alter while adjusting if its a long way out.

    All this is pointless if the choke is stuck.
     
  10. mikealston2428
    Joined: Jul 2011
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    Location: aussie

    mikealston2428 Senior Member

    Hi Frosty,
    I replaced the dizzy awhile back but dont think i set the timing correct at that time, so will need to reset it.

    I understand this is not related to the black smoke/soot problem.

    I had alook on utube, i am taking the boat out tomoro so once the motor has been running and warm i will take the top off and see if the choke flap is open or closed.

    should it be fully open or closed when warm ?

    Many thanks,
    Mike
     
  11. Frosty

    Frosty Previous Member

    Open.
     

  12. mikealston2428
    Joined: Jul 2011
    Posts: 188
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    Location: aussie

    mikealston2428 Senior Member

    Hi All,

    I sorted black smoke problem.

    The choke plate was staying closed, the bar corrected to the temp spring and plate had fallen off, small locater ring came off causing the plate not to open.

    Nice and simple lucky.

    Thanks for your help.

    Mike
     
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