2001 Merc 350 Mag MPI White Smoke

Discussion in 'Sport Cruisers' started by Joe Poznanski, Nov 16, 2018.

  1. Joe Poznanski

    Joe Poznanski New Member

    2
    Nov 16, 2018
    2001 SeaRay 280 Bowrider
    2 x 350 Mag MPI w/Bravi I Outdrives
    Lets start with a background. I bought the boat in March 18' and I noticed there was a small amount of white smoke coming from the starboard engine. It ran and still runs great, but the white smoke has intensified. This intensification occurred in a matter of two outings. This occurs from start-up to when I return for the day. It leaves a sheen in the water which makes me think it is gas. There is no white smoke coming from the port engine so that rules out water in the gas. Plus, I just changed the fuel filter and there was no separation/debris when I poured it into a clear bottle. The compression is high in all 8 cylinders ranging from 180-193. There was soot on all 8 spark plugs which affirms the no water theory. This makes me think it could be a cylinder that isn't completely combusting all the fuel. How do I figure out which one it is?
     
  2. Craig

    Craig Active Member GOLD Sponsor

    241
    Feb 8, 2007
    Maryland
    2006 320 Sundancer
    twin 350 Horizon V drives
    Have you changed the plugs,wires and dist
    Cap lately?
     
  3. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    White is steam from water. Soot on plugs would be blackness out exhaust. You may have 2 issues here.
     
  4. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    PA
    Various
    Various
    Compare the plugs - google "how to read a plug". If there's a difference in how one cylinder is operating, there will most likely be evidence in the way the plug looks.

    Do the engines have closed cooling?
     
  5. Joe Poznanski

    Joe Poznanski New Member

    2
    Nov 16, 2018
    2001 SeaRay 280 Bowrider
    2 x 350 Mag MPI w/Bravi I Outdrives
    Hey guys thanks for the feedback. I just changed cap, rotor, plugs and wires. Also changed MAP sensor. I still have white smoke. Might take it to a local marina...idk what else I can do
     
  6. Espos4

    Espos4 Active Member

    580
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Good compression on all cylinders and normal amount of soot on the plugs tells me that the cylinders appear to be ok and not ingesting water.

    This could possibly be clogged manifolds and/or riser, creating hot spots where exhaust water boils instead of being pushed out as a liquid.

    How are your manifold and riser temperatures?
    Can you keep your hands on he risers or are they too hot?

    Another possibility is a cylinder head crack in the exhaust port. Cooling water could be entering the exhaust stream at a very hot area.

    I would remove the manifolds and take a look at the exhaust ports.

    You still haven’t answered the fresh/raw water cooled question.
     
  7. WV 320 Dancer

    WV 320 Dancer Active Member SILVER Sponsor

    169
    Oct 28, 2018
    2003 Sea Ray Sundancer 320
    Twin 350 MAG - V Drive
    White smoke tells me water. A leak down test will tell you if you have a head gasket problem. If so then there is your answer. As others have stated the issue could be downstream from the engine.
     
  8. douglee25

    douglee25 Well-Known Member

    Jan 13, 2008
    NJ
    Boatless
    Big ones!
    With water temperatures dropping it could likely be steam.
     
  9. Espos4

    Espos4 Active Member

    580
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    That doesn’t explain why it only happens to one motor and not the other.
     

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