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  1. #1

    Default Mercruiser 496 Cooling Discussion: see attachment also

    OK. Get the popcorn as this may end up being a long thread. Ifyou get annoyed by me asking multiple questions to responses, this thread maynot be for you. What we have here is a Merc 496 MAG (base) with a Bravo III duoprop outdrive. 1/2 system. I have done quite a bit of research on how towinterize this engine. 6 million different answers, techniques, procedures.Before devising a plan for winterizing, I need to understand the basics of whatI am actually "doing" when winterizing this thing. Attached is thepertinent information on the boat, along with a cooling diagram I believe to becorrect for my engine. Good starting point. The original diagram did not have akey to the numbers so I searched and came up with (I think), the correctnumber/description. Correct me if I am wrong.
    No need to chime in on the things I already know:
    With 1/2 system, no need to drain the radiatorfluid (it was changed last year).
    It has the blue air pump system drain.
    It looks to have a manual 3 point drain system(2 for seawater pump/1 water drain going to heat exchanger).

    As stated, you cannot apply a winterizing technique for thisengine unless you understand the basic operation of the cooling system. This iswhere I am at now. Below are questions that need answered before deciding on a"winterizing technique".

    1. Starting at the red arrow, I follow the "lakewater" hollow arrows. Lake water comes infrom the drive to the inlet hose, through the seawater pump, out the outlethose around the back of the engine through the oil cooler, passes through thewater drain assembly. This is where I am getting stuck. It "looks"like it then passes through the heat exchanger to the port side then out theport exhaust manifold and exhausted overboard. Correct/Incorrect? The nextquestion (see red question mark on diagram) is the lake water looks to"turn around" in the heat exchanger and pass through the starboardexhaust manifold. Is this correct?

    2. The crossover and circulating pump look to only circulateethylene glycol and both of these do not seem to circulate any lake water. Isthis correct?

    3. What are we protecting when we "winterize" thisengine? It looks like we are avoiding freezing of the following components:
    Both exhaust manifolds
    Heat exchanger
    Oil Cooler
    Seawater Pump
    Correct or incorrect?

    4. Since the engine block is trulyclosed to any "lake water", and the radiator fluid has been changedand at the appropriate level, I am to assume there is no worries concerningcracking the engine block as there is no "lake water" going to theactual engine, only ethyl glycol. Correct?



    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    the heat exchanger will have 2 outlet lines that go to the bottom of the manifolds and 1 water inlet line. there will be a drain plug on the heat exchanger to drain the raw water side or remove the inlet hose and suck or blow with a shop vac.
    Water flows from the drive thru the coolers to the heat exchanger out the exchanger to the bottom of the manifolds and out the risers..
    Personally do not like the quick crack system so I remove the hoses and drain the raw water side manually, also remove the plugs from the cool fuel, power steering, oil cooler and raw water pump to drain everything.

  3. #3
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    Sep 2008
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    to expand on what Doc said, the 'lakewater' flows into the HX which has two outlets, one for each exhaust manifold....

    for 2), yes and, hopefully, the antifreeze has been mixed with distilled water, 50/50, adjusted for your location.

    for 3), the winterization process is to protect the 'lakewater' side from freezing.

    for 4) as long as the coolant mixture provides an adequate freeze point and proper pH, you should be good to go.

  4. #4

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Click image for larger version. 

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    Ok. Explain which hoses transport water where and the direction of the water. I think the top one is to the radiator.

  5. #5
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    referencing the HX pic, starting at the bottom left, going CCW, you have 1) raw water out to exhaust manifold, 2) coolant out to crossover, 3) coolant in from crossover, 4) raw water in (90 deg) , 5) raw water out to exhaust manifold, and 6) coolant to expansion tank....

  6. #6

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Excellent. I appreciate your help. On plane to work. Will send what " i think" is a straght forward winterization procedure soon.

  7. #7
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    what's wrong with the factory procedure?

    if you want to tailor it and understand the risks with changing it....go for it....

  8. #8

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    it's not that anything is wrong with it. I just haven't looked at it closely. I have heard everything from antifreeze through muff, just do the quick drain (of which I won't do), run a magic wand over it, call on Joe Boo, etc. Since I am dealing with an expensive boat, I want to double check everything + I like learning stuff.

  9. #9
    Join Date
    Sep 2010
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Quote Originally Posted by makomark View Post
    what's wrong with the factory procedure?

    if you want to tailor it and understand the risks with changing it....go for it....
    I agree. Do it the factory way.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  10. #10

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    OK. Looks like two of you guys who have experience recommend using the actual manual drain procedure direct from the Service manual. Well, here is is (attached).
    A few notes before proceeding:
    1. I will run the engine with the correct amount of fuel stabilizer and allow it to warm up to operating temperature (160 on my boat) and let it work it's way through the system.
    2. Do a oil and fuel filter change.
    3. Change the stern drive oil
    So... here we go..
    Basically I will do the single point drain system procedure as outlined in the steps, followed by, and in addition to doing the manual drain procedure as per the steps.

    As stated, I believe my boat has only three manual drain plugs. Two for the seawater pump and one on the right side below. These are the only three drain plugs I am aware of. I will double check to see if there is one on the cool fuel cell.

    According to you (the experts), that's it aka follow the steps 1-11. No "extra steps" such as pulling hoses and pouring poly glycol.Pages from Merc 496 Owners Manual.pdf

  11. #11
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    You will have to run the engine a long time to get your treatment through to the injectors.

    DO NOT USE THE AIR VALVE, IT MAY NOT CLOSE. Drain it manually.

    The engine is fresh water cooled. You are just anti-freezing the heat exchanger, the fuel module, the water pump, coolers and the exhaust.

    I disconnect the quick connect (if equipped) between the pump and the transom and pump my antifreeze in(engine running) until it comes out of the exhaust undiluted.

    IMO, I would pay a pro to winterize your engine. A legitimate Pro. So it is done right. Best $200-250 you will spend.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  12. #12
    Join Date
    May 2010
    Location
    DC Burbs/Maryland Eastern Shore
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    You don't need to run fuel stabilizer all the way to the injectors. Just put some in the tank if that makes you feel better. Honestly if it's just over a few cold months of winter, fuel stabilizer isn't going to help, or hurt. If it were going to be sitting for 6-8 months or more, then I'd have the tanks drained.
    Practicing the ancient art of ren-ching

  13. #13

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Chris. Thanks for your helpful reply. I will sort of take your advice. My buddy who works on my boat is a legit Pro with his own marine repair business. He has more business than he can handle anyway so I will do it with him to make sure I do it right before doing it myself next year.

  14. #14
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    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Quote Originally Posted by jigeye View Post
    Chris. Thanks for your helpful reply. I will sort of take your advice. My buddy who works on my boat is a legit Pro with his own marine repair business. He has more business than he can handle anyway so I will do it with him to make sure I do it right before doing it myself next year.
    That is the best way.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  15. #15

    Default Re: Mercruiser 496 Cooling Discussion: see attachment also

    Chris. Thank you for your sage advice.

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