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  1. #1
    Cadet
    Join Date
    Jun 2005
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    Nova Scotia Canada
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    25

    Default 5.7 Thermostat Housing Replacement

    I am new to the posting, but have been reading the forums for a couple of years. What a great site to share information. I am rebuilding a 5.7 Mercruiser which is around a 1987 with a Bravo 2 stern drive. The boat is a 1990. My thermostat housing was badly rusted. I purchased a new thermostat housing which is a newer styled. From what I am told it is the replacement style for the style that was on it as the original style was causing a lot of problems.
    The original one that was on it was a single piece unit with 6 hoses. Two of them had check balls with a spring. The replacement unit has the same amount of hose attachment points but it is a two piece unit. I believe the comparible Mercruiser p/n to the replacement one I have is 87290A23. My problem is that the engine water pump has a hose fitting at the 12 o'clock position which hits the housing and prevents the housing from sitting flat. The original housing did not stick out so far forward allowing clearance for this fitting. Has anyone come across this problem and what is the solution?
    Second part of the question which may sound kind of dumb, but the fitting at the 12 o'clock position on the water pump..what is it for and where does the hose go? I took this engine apart almost two years ago and for financial reasons took my time slowly putting it back together. I took lots of pictures and labelled almost everything, but can't find the hose that goes on this fitting.
    I really appreciate any help that can be provided. Thank you muchly.

  2. #2
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
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    The Mouth of the Chaumont River, Ny.
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    52,594

    Default Re: 5.7 Thermostat Housing Replacement

    The original one that was on it was a single piece unit with 6 hoses. Two of them had check balls with a spring. The replacement unit has the same amount of hose attachment points but it is a two piece unit. I believe the comparible Mercruiser p/n to the replacement one I have is 87290A23. My problem is that the engine water pump has a hose fitting at the 12 o'clock position which hits the housing and prevents the housing from sitting flat. The original housing did not stick out so far forward allowing clearance for this fitting. Has anyone come across this problem and what is the solution?
    Ayuh,... Put an angled fitting in that hole, instead of a straight 1...
    Second part of the question which may sound kind of dumb, but the fitting at the 12 o'clock position on the water pump..what is it for and where does the hose go? I took this engine apart almost two years ago and for financial reasons took my time slowly putting it back together. I took lots of pictures and labelled almost everything, but can't find the hose that goes on this fitting.
    If you've got a cabin heater, or water heater, or whatever, it's Usually a return water fitting...
    Any Grease is Better,..... Than No Grease at All.......

  3. #3
    Cadet
    Join Date
    Jun 2005
    Location
    Nova Scotia Canada
    Posts
    25

    Default Re: 5.7 Thermostat Housing Replacement

    You are the man! I looked in the boat and found the hose tagged that goes to the top of the engine water pump. It is for the water heater. That is why I couldn't find it in my box of parts. Once I put an angled fitting on, I should be good. Thank you

  4. #4
    Petty Officer 2nd Class
    Join Date
    Aug 2011
    Posts
    185

    Default Re: 5.7 Thermostat Housing Replacement

    Hey tailwind, do you recall where you found the information about your old housing having check balls in it?

    B/c mine was dirty and rusted annnnd I just sandblasted it and painted it.....

    Want to see if my style was included in the information.

  5. #5
    Cadet
    Join Date
    Jun 2005
    Location
    Nova Scotia Canada
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    25

    Default Re: 5.7 Thermostat Housing Replacement

    My old housing still had the check balls in it. When I went to Nova Automotive in Dartmouth N.S., they showed me the replacement style thermostat housing. They said the original one had a design flaw that would leave voids in the flow of the water causing the pump to sometimes cavitate leading to overheating of the engine. This place deals with a LOT of engines, and the marina is right across the street. They seem to know their business so I took their word for it and bought the new style. I did do a search on google and came up with the replacement mercruiser style p/n that I listed above. The new style still has the balls, it is just a bit longer in length.
    My problem now is that an angled fitting would work great if I could find one. I have been to several places some specializing in fittings but I haven't found any that will give me a 3/4" pipe thread on the bottom with an angled 5/8 hose barb on the top. I may have to leave my water heater out of the loop for now and just plug the water pump with the plug that was in it when I bought it.

  6. #6
    Moderator Bondo's Avatar
    Join Date
    Apr 2002
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    Default Re: 5.7 Thermostat Housing Replacement

    My problem now is that an angled fitting would work great if I could find one. I have been to several places some specializing in fittings but I haven't found any that will give me a 3/4" pipe thread on the bottom with an angled 5/8 hose barb on the top. I may have to leave my water heater out of the loop for now and just plug the water pump with the plug that was in it when I bought it.
    Ayuh,.... On the Intake Manifold, just aft of the T-stat housing, you'll see a 1/2" pipe plug....
    Pull that plug, 'n use that port for yer water heater feed line....

    That's where it's Supposed to be anyways....
    Any Grease is Better,..... Than No Grease at All.......

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