1989 Sea Ray Weekender 454, closed cooling system stbd eng overheating.

Discussion in 'Classic Sea Rays' started by vanman59, Jun 27, 2020.

  1. vanman59

    vanman59 Member

    51
    Sep 13, 2015
    NC
    30' 1989 Sea Ray Weekender
    1992 Dodge W250 Cummins W/auto trans
    Twin Merc 454s
    It overheats when under power. At home running on a water hose temps run 145 degrees at idle. Here's what I've done since early last year: freshwater impellor ( impellor was fine, pliable not broken), engine water pump, cleaned heat exchanger for water cooling, 145 degree thermostat both manifolds and risers (port manifold rusted thru at #3 exhaust - not into water jacket but into bilge. Stbd manifold had evidence of water leaking into exhaust ports - presumably from manifold itself). Here is the wierd part; after replacing the port manifold we filled the heat exchanger with water and a weird thick black soap bubble like stuff came bubbling out so we tried just flushing it out (just running overflowing water in the heat exchanger) with eng running and the water was black. We also found the choke hadn't been working so fixed that. I am beginning to wonder if the block has soot in it from running rich for who knows how long and that's impeding the heat transfer in the engine. We ran the boat for a couple of years with no problem and don't think there are any impellor parts in the cooling system. How can I test the raw water volume at idle? Should it fill a 5 gallon bucket in 30 seconds?
    Any help is appreciated, the port engine runs at 145 to 165. I'm beginning to think I need to dismantle my raw water cooling system and inspect and flush. Does that require pulling manifolds? They aren't too bad now, I broke 3 bolts on the port side but was able to get them out.
     
    Last edited: Jun 27, 2020
  2. vanman59

    vanman59 Member

    51
    Sep 13, 2015
    NC
    30' 1989 Sea Ray Weekender
    1992 Dodge W250 Cummins W/auto trans
    Twin Merc 454s
    I just got to thinking and wondering if someone before me put some "head gasket" in a can in the motor and it finally crapped out? Almost forgot oil fine eng runs a 3800 rpm easily now that choke is fixed, I think it may have been a little short of that mark before.
     
    Last edited: Jun 27, 2020
  3. vanman59

    vanman59 Member

    51
    Sep 13, 2015
    NC
    30' 1989 Sea Ray Weekender
    1992 Dodge W250 Cummins W/auto trans
    Twin Merc 454s
    Update- checked the heat exchanger pressures with a radiator tester. Results:
    Stbd (over heating motor) pumped up to 16 PSI. It took 12 minutes to go down to 10 PSI. Released pressure to zero then started motor. Ran at idle, it took 8 minutes to get to 145 degrees and 7.5 PSI. held steady, no spikes.
    Port (good motor) pumped to 16 PSI. It took 4 minutes to drop to 10 PSI. Released pressure to zero started motor. Ran 11 minutes to get to 145 degrees and 11 PSI.

    Seems like the motor is holding pressure, no head gasket leaking or cracks.
     
  4. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    new manifolds, risers, waterpumps and an unobstructed water supply. Right?
     
  5. dwna1a

    dwna1a Well-Known Member GOLD Sponsor

    Apr 23, 2012
    James River
    88 Weekender 300 "Seahorse"
    Twins 350
    If I'm reading this right you have I/O's? Have you back flushed the cooling system?
     

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