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  1. #41
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    41,010

    Default Re: no water! - it isnt the impeller

    Quote Originally Posted by stu9000 View Post
    I have ordered one.


    I cleared the holes in the cooling block but did not check the actual exhaust. Do you mean here?


    Next time I'm open the boat I will...
    Check the exhaust
    Fit the thermostat
    Run acid cleaner through the engine on a loop

    Thanks Vic and everyone else. It is very much appreciated.

    S
    Yes and right through the exhaust outlet elbow and into the exhaust gas stream

    Not sure what you mean by the "cooling block" though.

    The trouble with trying to clean a cooling system like this with acid is that if any parts are completely blocked the acid wont get to them and they don't therefore get cleaned.

  2. #42
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    5,051

    Default Re: no water! - it isnt the impeller

    Quote Originally Posted by VicS View Post
    Yes and right through the exhaust outlet elbow and into the exhaust gas stream

    Not sure what you mean by the "cooling block" though.

    The trouble with trying to clean a cooling system like this with acid is that if any parts are completely blocked the acid wont get to them and they don't therefore get cleaned.
    That's the point of the Rydlyme that was discussed earlier, it goes round and round for 2 or 3 hours and clears everything it touches. It won't do the exhaust elbow, because the pipe going to that has to go back to the bucket of Rydlyme, but that can be manually cleaned, then soaked in the bucket whilst it's circulating.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  3. #43
    Join Date
    Mar 2008
    Location
    near kingston upon thames, surrey
    Posts
    358

    Default Re: no water! - it isnt the impeller

    Quote Originally Posted by VicS View Post

    Not sure what you mean by the "cooling block" though.

    .
    My bad. I mean to say the exhaust manifold.

  4. #44
    Join Date
    Mar 2008
    Location
    near kingston upon thames, surrey
    Posts
    358

    Default Re: no water! - it isnt the impeller

    What I still don't get is if the thermostat is not there=the engine running cool.
    Should it not be the other way around?

    If I have this right when the stat is open it follows the red path, otherwise it goes the long route through the engine cooling channels.
    .
    Screenshot_20180424-223244_1.jpg

    If there is no thermostat present surely the short cut route is open, so the engine isn't being cooled = running hot.

    The blue arrow just indicates cold water being pumped towards the engine. There is a pipe half way along that blue line feeding into the engine without going via the thermostat. This seems counter intuitive but perhaps even a cold engine needs some water flowing around it. Either that or I still have a lot to learn

  5. #45
    Join Date
    Oct 2007
    Location
    Poole
    Posts
    1,657

    Default Re: no water! - it isnt the impeller

    Quote Originally Posted by stu9000 View Post
    What I still don't get is if the thermostat is not there=the engine running cool.
    Should it not be the other way around?

    If I have this right when the stat is open it follows the red path, otherwise it goes the long route through the engine cooling channels.
    .
    Screenshot_20180424-223244_1.jpg

    If there is no thermostat present surely the short cut route is open, so the engine isn't being cooled = running hot.

    The blue arrow just indicates cold water being pumped towards the engine. There is a pipe half way along that blue line feeding into the engine without going via the thermostat. This seems counter intuitive but perhaps even a cold engine needs some water flowing around it. Either that or I still have a lot to learn
    no thermostat provides no controlled blockage so cooling circulates even when engine is cold.
    hence engine runs colder than it should.
    with thermostat the engine passage is blocked in favour of the bypass until the engine gets warm, then the thermostat opens and allows coolant to engine... but only when needed.

  6. #46
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    41,010

    Default Re: no water! - it isnt the impeller

    Quote Originally Posted by stu9000 View Post
    What I still don't get is if the thermostat is not there=the engine running cool.
    Should it not be the other way around?

    or I still have a lot to learn
    Yes you seemed to have failed to understand the circulation, despite the diagram in the manual

    Cold water flows directly into the engine at two points, one near the back of the manifold and one via the bottom connection on the thermostat housing. The thermostat does not control the cold water entering the engine, it controls the hot water leaving ( just as the thermostat in your car engine controls the hot water flow from the engine to the radiator).

    When the engine is cold the thermostat is closed . No water leaves so effectively no water flows through the engine.

    When the engine reaches its operating temperature the thermostat opens to allow hot water to leave, then of course you get a flow through the engine. Cold water entering directly and hot water leaving via the thermostat.

    The hot water flows along the line of the red arrows to the exhaust outlet elbow

    AS WELL AS this flow through the engine there is also a flow through the bypass in the thermostat housing. This flows even when the thermostat is closed, bypassing the engine and the thermostat, in order to cool the exhaust whlie the engine is warming up, other wise the exhaust system would burn up in the period before the thermostat opens

    I have added more detailed colouring to the water flow diagram in the hope that it will help.

    MD7A cooling.JPG
    Last edited by VicS; Today at 00:08.

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