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    over heating-gctid811986

    Need some help or ideas of what I could be missing. I have a 1988 2455 with a 305 chevy with omc out drive. Got the boat last year had a cracked block got a new used motor, tore that down to the block. Didn't take crank pistons or cam out. Every thing looked good there. Put it all back together ran it outside the boat with water directly to the thermostat ran great. Got it in the boat and it overheated. Changed thermostat changed impeller. Still over heated so took the lower unit off changed all of the seals in the lower half. Except didn't pull prop shaft. The water pickup tube grommets where in bad shape. Any how hooked it up on the muffs ran at 175 for about 20 to 30 minutes. Took it down to the lake and over heated again.
    1988 bayliner 2455 ciera sunbridge

    #2
    "remote6" post=811986 wrote:
    Need some help or ideas of what I could be missing. I have a 1988 2455 with a 305 chevy with omc out drive. Got the boat last year had a cracked block got a new used motor, tore that down to the block. Didn't take crank pistons or cam out. Every thing looked good there. Put it all back together ran it outside the boat with water directly to the thermostat ran great. Got it in the boat and it overheated. Changed thermostat changed impeller. Still over heated so took the lower unit off changed all of the seals in the lower half. Except didn't pull prop shaft. The water pickup tube grommets where in bad shape. Any how hooked it up on the muffs ran at 175 for about 20 to 30 minutes. Took it down to the lake and over heated again.
    You sound like you have enough skill such that this won't be too hard. You would probably be advised to get a water flow diagram and simply follow it through inspecting every point on the water flow. It doesn't take too long. If the flow path is good then there isn't really too much else to worry about. The circulation pump is easily removed for inspection (new gasket required). I'll dig out a water flow diagram and post it.

    Water flow diagram . . .

    [attachment]37222 wrote:
    rwc-half-flow.jpg[/attachment]

    If you want to see whether water is getting picked up from the outdrive properly, you can disconnect the feed hose at the thermostat and make sure you get a real whoosh of water when the engine is started (for a very short period).

    Do that 1st, when that is checked just follow the flow making sure that it is all clear and flowing. The thermostat can be boiled in a pan to make sure that it opens. Make sure, when you are in there, that the PO has assembled the thermostat parts the right way round (as per the diagram).

    If you take the circulation pump off, make sure that the spindle has not become disconnected or loose from the internal impeller. I had one where you could hold the impeller in one hand and spin the pulley in the other. That one had me fooled for a while.

    G'luck. We have all been there.
    Terry (Retired Diving Instructor and Part Time IT Consultant)
    1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
    MMSI 235061726

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      #3
      No muffs,

      Submerge in a big tub or take her back to the lake, undo the transom raw water hose,

      Perform a raw water flow test first.
      Joon, Kathy, Jaden & Tristan
      Uniflite 42 AC, DD 671N
      93 3058 sold
      92 2855 (day boat)
      91 Fourwinns 205 (lake boat)
      Longbranch WA
      Life is Good

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        #4
        I had the same problem with my previous boat that had an OMC Cobra. The omc uses a power steering cooler located under the port exhaust manifold and when the impeller comes apart it will clog up the small tubes with chunks of rubber.
        1988 Mainship 36 Sedan
        1995 2858
        1988 2655
        1987 2150
        Commercial/Industrial HVAC Service Tech.

        Comment


          #5
          "remote6" post=811986 wrote:
          Need some help or ideas of what I could be missing. I have a 1988 2455 with a 305 chevy with omc out drive. Got the boat last year had a cracked block got a new used motor, tore that down to the block. Didn't take crank pistons or cam out. Every thing looked good there. Put it all back together ran it outside the boat with water directly to the thermostat ran great. Got it in the boat and it overheated. Changed thermostat changed impeller. Still over heated so took the lower unit off changed all of the seals in the lower half. Except didn't pull prop shaft. The water pickup tube grommets where in bad shape. Any how hooked it up on the muffs ran at 175 for about 20 to 30 minutes. Took it down to the lake and over heated again.
          Did you fix it?
          Terry (Retired Diving Instructor and Part Time IT Consultant)
          1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
          MMSI 235061726

          Comment


            #6
            The OMC impeller replacement is a finicky task. If you do not use the OEM part from Bombardier and you dont seat the rubber ring correctly the drive will suck air while underway. It will run fine at idle but as soon as you throttle up your engine will begin to overheat. Get the OEM kit not an aftermarket one and apply a small amount of silicone to hold the rubber gasket in place.

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              #7
              Also:

              Before you water test the boat; run the engine on the water muffs with the plastic cover off; and look all around the impeller housing. If you see any water leaking out either the gasket is not in right or you need to slightly tighten the bolts for the housing a little more. I use OMC triple guard grease (a thick waterproof grease) to hold that o ring gssket in place.
              88 Four Winns 200 Horizon 4.3 OMC
              98 Jeep Grand Cherokee 4.0/Selectrac
              07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

              Long Island Sound Region

              Comment


                #8
                If you look at the diagram TerryW added, water from out drive comes in to a strainer, then to Tstat. Or as RPrather pointed out, there may be a cooler. Either way, there is a removeable cover to allow cleaning (if it's a strainer). This may be clogged.

                When you ran engine with water hose directly to Tstat, you bypassed the strainer (the clog lol), and that's why it didn't overheat.

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