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  1. #1
    Seaman
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    Sep 2005
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    Default water jackets clogged!

    HII have discovered why my engine overheats; the water jackets are filled with sand and rust.The engine is a 460, and viewing from the freeze plugs(3 per side) reveals that it is about half full of the stuff. I have managed to get most of the material out using my fingers and a shop vac about an inch around each plug. My question/problem is: how do I clean the rest of it out that is at the front of the engine and the back? is the water jacket continous around the block as I suspect it is, or is it just on the sides? I don't want to have the engine hot tanked because I don't really know how to rebuild an engine.thanksJosh

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: water jackets clogged!

    Yes, the water jackets go all the way around the cylinders. It keeps the cylinders equally cool. Hot spots are worse than all the engine hot.Your problem is one of the major problems with raw water cooled engines, and when they get plugged up, they have to be cleaned out ALL THE WAY AROUND.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
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  3. #3
    Seaman
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    Default Re: water jackets clogged!

    how do I clean it all the way around then>?

  4. #4
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: water jackets clogged!

    Hate to say this, but I'm not sure if it's even possible. If I were you, I would be looking for another engine.Your problem is one of the facts of life of a raw water cooled engine. They corrode, and plug up.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  5. #5
    Seaman
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    Sep 2005
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    52

    Default Re: water jackets clogged!

    hi,is it possible to pop the heads off and have the engine "hot tanked?" but leave the rest of the engine assembled?if not, to save money, is it possible to carefully label all bearings, pushrods, etc. and reuse them after hot tanking>?will hot tanking remove all this stuff?

  6. #6
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: water jackets clogged!

    is it possible to pop the heads off and have the engine "hot tanked?" but leave the rest of the engine assembled?
    Absolutely NO!!!
    if not, to save money, is it possible to carefully label all bearings, pushrods, etc. and reuse them after hot tanking>?
    Yes, if the bearings are any good. But the block has to be empty of EVERYTHING. Crank, pistons, lifters, if it's bolted to it, it has to come off.But there is still the chance the hot tank won't get all the corrosion and sand out of it.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  7. #7
    Petty Officer 1st Class
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    Nov 2005
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    richmond area VA.
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    320

    Default Re: water jackets clogged!

    One option U have is to run the engine with the block drain petcocks opened and with a screwdriver,un-clog each of them till they flow freely then run the boat hard as long as u can without sinkin it! (Go bilge pump!)Keep an eye on the temp!

  8. #8
    Lieutenant Commander mkast's Avatar
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    Default Re: water jackets clogged!

    i/o waldoYou are telling this guy to run the engine with the drains open... when will the thermostat open?Even if the drains are flowing freely, how can he tell how much debris is still left in the block? When was the last time you did this???JoshYou can either run the engine the way it is, ordisassemble the engine.
    From Mercruiser:
    Anyone who uses a service procedure and/or tool, which is not recommended by the manufacturer, first must completely satisfy himself that neither his nor the productís safety will be endangered by the service procedure selected.

  9. #9
    Petty Officer 1st Class
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    richmond area VA.
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    Default Re: water jackets clogged!

    Four times last summer at the marina I work at.We get a lot of problems with silt/sand buildup in the water jackets in the brackish river here.Works fine every time!Run the engine till warm,open drains,haulass till you r about to sink!Who knows if it completly flushes the jackets.Either this or pull the engine to be SURE!(With a good inpeller,there is more than enough cooling water to both flush & cool.)

  10. #10
    Petty Officer 1st Class
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    Mar 2005
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    three oaks, mi
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    317

    Default Re: water jackets clogged!

    well......................i guess you can try to do that, and take the chance of sinkin' it............WHATEVER!!!!!! sounds a little crazy to me...i agree with don

  11. #11
    Petty Officer 1st Class klos's Avatar
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    Oct 2005
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    Default Re: water jackets clogged!

    In both of my auto repair shops we have a tool called a flush gun. A garden hose hooks to one connection and air hose to the other for regulated compressed air. We use the pressurized air and water to flush cooling systems and heater cores and have cleaned some pretty nasty/rusty cooling systems with great success. If the debris is somewhat loose (not solidified) this method will work.

  12. #12
    Petty Officer 1st Class
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    Nov 2005
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    richmond area VA.
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    320

    Default Re: water jackets clogged!

    THAT sound like the gadget MADE for this fix!!Can it be adapted to a raw boat?

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