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Mercruiser 350 mag mpi on 2005 285

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    Mercruiser 350 mag mpi on 2005 285

    Hi I am having engine over heating issues on my boat, I am in UK. Second time this happened and had to be towed back. have been researching and there is no issue with Reed filter. Understand it could be risers rusted up .Not sure what references are to water Jackets in these?

    Next issue could be water pump . I have read you can get a wear plate. Mine is a brass pump but not sure what wear plate to get. Not clear when I search internet. I want to have it so it can be done same time as changing impeller.

    any advice greatly appreciated.

    #2
    How old is the raw water pump impeller? This is a maintenance item that Mercruiser recommends be replaced every 2 years. Is the boat equipped with a Bravo drive? If so another know cooling issue is the transom assembly cooling hose getting blocked with marine growth.
    1997 Maxum 2400 SCR 5.7LX Bravo II

    Mike

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      #3
      ........
      Originally posted by Grantplant View Post
      Hi I am having engine over heating issues on my boat, I am in UK. Second time this happened and had to be towed back. have been researching and there is no issue with Reed filter.
      Understand it could be risers rusted up .Not sure what references are to water Jackets in these?
      In my opinion, riser/spacer seawater transfer ports are seldom the main issue.

      I would focus on the seawater transfer ports within the Exhaust Elbows. These can often be cleaned up and re-used.

      I'd also look at the Elbow's ports that lead the "spent" seawater into the exhaust mixing chambers. These can also become restricted with rust scale.


      Next issue could be water pump .
      Since it's doubtful that your 350 Mag is equipped with an A drive, there will be two pumps on your engine.
      ..... seawater pump
      ..... coolant circulating pump.



      I have read you can get a wear plate. Mine is a brass pump but not sure what wear plate to get. Not clear when I search internet. I want to have it so it can be done same time as changing impeller.
      Are you asking about a seawater pump impeller "cam"?
      Merc uses an eccentrically positioned impeller. In other words, there will be no cam.
      There will also be two thrust surfaces within the pump body.



      any advice greatly appreciated.

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      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Comment


      • Nauti_Mike
        Nauti_Mike commented
        Editing a comment
        Being a 2005 it may have dry joint exhaust

      #4
      Hi had a leg an engine service last year with impellers changed. What I have read it should be dry joint as 2005 but not sure what this means. It has a bravo 2 leg. Looking for most common reason for overheating so I can start there and move on .boat is coming out of the water this week. I have been reading the brass raw water pumps are only good for around 200 to 300 and the brass get scored . This is when you can get a wear plate to make somethi again.

      Comment


        #5
        Reading your comments regarding two pumps and I right in saying that the engine both water cooled through raw water pump and coolant working side by side? Pretty new to all this and trying to learn

        Comment


        • builderdude
          builderdude commented
          Editing a comment
          Likely a closed cooled system. Yes seawater cools the closed side via the heat exchanger.

        #6
        What is happening exactly? Overheating at higher rpm only or overheating after 20 minutes at idle rpm?

        You can start with a in the water flow test to verify your seawater pump is producing enough flow.
        Bravo engine mounted seawater pump should produce 7.5 U.S. Qt. in 15 seconds at 1000rpm. You've stated yours is brass, is it a crank mounted pump? Post a pic of it.

        When you perform the test take a look at anything seawater path related to ensure there are no restrictions. ie sea strainer (if equipped), oil cooler, all hoses, heat exchanger tube bundle, exhaust etc.

        Is the engine equipped with a full closed cooled system? or part closed? Post a pic of your engine showing the cooling hose routing etc.

        When the boat is out of the water you may want to check the inner transom mounted water fitting area for corrosion (Bravoitis) and verify the water path from the intake in the leg up to that water fitting is unobstructed.
        Dave
        Edmonds, WA
        "THE FIX"
        '93 2556
        Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
        Misc. projects thread
        https://www.baylinerownersclub.org/f...56-gctid789773

        Comment


        • Nauti_Mike
          Nauti_Mike commented
          Editing a comment
          Agree, perform a flow test.

        #7
        It is at idle 20 mins as stated. I will get some pics when I go up. Thanks

        Comment


          #8
          I’d be tempted to replace the t stat just to rule that out, then verify the seawater pump flow.
          Dave
          Edmonds, WA
          "THE FIX"
          '93 2556
          Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

          The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
          Misc. projects thread
          https://www.baylinerownersclub.org/f...56-gctid789773

          Comment


            #9
            We had exactly the same problem and it really had me scratching my head. Eventually I found the culprit when I took off the end caps of the heat exchanger. Some mussel shells had gotten in there and were restricting the amount of water flow. I simply took a hose and flushed it out and everything was fine. A quick little five minute check for you, and you could eliminate that from the long list of things that could possibly be causing this.
            2014 Double Eagle 176EXL. But we are not done with Bayliner yet…this is just to get us to and from our cottage in the Gulf Islands.

            Comment


              #10
              Our marina had a head scratcher with an overheating Merc 470. After hours of trouble shooting the problem turned out to be a brand new Mercruiser thermostat that wouldn't open.
              2007 Discovery 246
              300mpi BIII
              Welcome island Lake Superior

              Comment


                #11
                That's great advice thanks. Was due to go up tomorrow but my son has just decided to feel unwell!

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