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Steam out of port upper exhaust 2005 341 Meridian-gctid394631

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    Steam out of port upper exhaust 2005 341 Meridian-gctid394631

    Hi all,

    I've got a friend with a 2005 341 Meridian (twin Cummings) and he gets steam coming out of the upper exhaust on the port side when running about 1500 RPM. It doesn't seem to steam at idle and doesn't seem to steam at 2500 RPM. The starboard side doesn't seem to steam at any RPM.

    The 341 has dual exhausts on each side. The primary exhaust is underwater and the upper exhaust is an idle bypass so the engine doesn't see the backpressure of the underwater exhaust when starting.

    Engine temps are normal and he's just had the impeller changed and the minicooler cleaned so it doesn't look like a lower water flow issue.

    Has anyone seen this before? Any suggestions?


    Jim V.

    This steaming at higher rpms sometimes means your seawater impeller is failing and not supplying enough cooling water to the heat exchanger. It could also mean your heat exchanger is fouled or you have a restriction in your seawater pickup. I am assuming you have a closed cooling system? What could be happening is the limited amount of cooling water is being overheated and turned to steam in the heat exchanger.


      Have him use one of those point and measure temp guns on his risers and other parts on both engines and compare temperatures. This should help him find the issue. Steam means either something is running warm in exhaust system and heating up cooling water too warm, or there is an internal leak somewhere leaking water into the exhaust via some pretty awful alternatives, like cracked exhaust, cracked head, bad head gasket, etc. Is he loosing antifreeze? If so, one of the awful alternatives might be in play. With the very highest speeds, the steam may just be so small that you do not see it.
      Started boating 1965
      Bayliners owned: 26 Victoria, 28 Bounty, 32, 38, and 47 since 1996


        I would take a thermo gun and use it to detect the temp differences between the 2 engines when one is steaming and the other is not. Find the hot spots and that should point you in the right direction.
        1997 3788/Cummins 6BTA 5.9 M2s (Sold)
        2003 Silverton 42c/Cummins 480CEs
        2019 Cobia 240 CC
        2006 Boston Whaler 13 Sport
        1985 3270/Hino 135s (Sold)

        Vero Beach, Fl.