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Thread: Steaming 350Q

  1. #1

    Default Steaming 350Q

    Hi Guys
    Have a little issue with the Stbd Thermocon 350Q in my 1975 35' Aft Cabin. Last fall I was coming back on the Main River when my buddy behind me called on the Radio to tell that my Stbd. engine seemed to be smoking from the exhaust. After inspection found that it was steam coming from the exhaust. Much more than on the Portengine.(Outside air temperature was about 40F.) Water flow seemed to be a little less, but as indicated water temperature was running normal I continued and planned to replace my impeller after docking.
    Next day I removed the impeller only to find it was still in good condition. I had replaced at the beginning of the season (5 months prior). I checked the raw water filter which was also OK. Now I was starting to runout of ideas. One of my buddies thought it might be a plugged riser or manifold.
    So...Now I have a brand new exhaust manifold with risers and still have a steaming exhaust. What I have noticed is that when I start up the engine everything is normal until the Thermostat opens. Now comes the extra steam.... Running out of Ideas again....Need help. Headgasket maybe????
    Lokking to hear your this,
    Johnscott

  2. #2

    Default Re: Steaming 350Q

    Seems to be the norm for these CC's. I replaced both risers and manifolds, new thermostat, new impeller, new circulatory water pump on my 251 with 350 a Mercruiser . It still blows some steam. I stopped worrying about it.

  3. #3
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,600

    Default Re: Steaming 350Q

    Is the thermocon still factory stock, i.e., with original log style manifolds and pressure relief valves in the elbows? IFSO, check for plugged/stuck relief valve.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

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