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Results 1 to 7 of 7
  1. #1
    Join Date
    Apr 2009
    Location
    Conestoga, Pa, USA
    Posts
    199

    Default "Who can give me some advice?

    "Who can give me some advice? I start my engine and if I leave it run at idle (700 RPMs) it heats up to over 180*. Then if I raise the RPMs to about 1500-1800 it drops right down to about 140*. Over the winter I had the empeller in the outdrive changed but it didn't help. Today I went to take out the thermostat and behold, there wasn't one in the system. I took a heavy bristled brush and scrubbed on the outdrive where the water intakes are but no help.
    Inside the engine compartment, the hose coming off the circulating pump and going to the fitting above the thermostat is cold as are the two coming off the exhaust manifolds. The other three hoses are vey hot.
    If anyone has any idea please help me out. Thank you, Bob"

  2. #2
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    2,754

    Default "[url=""]http://www.boatfix.co

    "http://www.boatfix.com/merc/Techbk/97/97hga6.pdf
    This link is the cooling system for mercs.
    The way you describe the hoses is confusing.water inlet should be right side at a angle.engine circ pump to therm housing, 2 hoses off the side of the therm go to the manifolds, 2 hoses from the cap go to the risers.
    witch ones are hot?"

  3. #3
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,329

    Default What year? Did you install a

    What year? Did you install a thermostat? W/o one the water can't mix and recirculate thru the engine. The T'stat hsg. is circulating hot water when it should send out warm water to the exhaust mans. The exhaust top hoses should be cold water and the bottom warm.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  4. #4
    Join Date
    Apr 2009
    Location
    Conestoga, Pa, USA
    Posts
    199

    Default "Thank both of you for your re

    "Thank both of you for your replys.
    Guy, It is a 1988, 350 Mercruiser (Chevy)@ 260 hp with a 4 barrel carb.I did not install the thermostat yet. As I understand you, it works opposite of a car. When you take the thermostat out of a car it runs cooler because the water is constantly circulating. On a boat, the water will not circulate unless the thermostat is in its' housing. Correct? If so, the thermostat may solve the problem.
    B.T.,The hose going to the circulating pump from the thermostat housing is hot. The 2 hoses going to the "risers" are also hot. The 2 hoses going to the exhaust manifolds are cold. Does this help any? Thank you, Bob G."

  5. #5
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    1,690

    Default "Thermostats are in all engine

    "Thermostats are in all engines, auto and marine to make sure the engine runs AT the temp that the designers want it to. Removing a T'stat under any condition is not a good solution.

    RE: the cold hoses to the manifolds. If the manifolds are more that couple of seasons old, or the impeller you removed had any pieces missing, you may have an obstruction that is preventing water flow to the manifolds."
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  6. #6
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,329

    Default ""The 2 hoses going to the

    ""The 2 hoses going to the "risers" are also hot. The 2 hoses going to the exhaust manifolds are cold."

    Do you have these two sets of hoses installed correctly? Per Bt Dr.: "...2 hoses off the side of the therm (warm water) go to the manifolds, 2 hoses from the cap (cold water) go to the risers."

    The T'Stat hsg. is the cooling system's mixing valve. W/o a T'Stat it just circulates hot water in the block. Put back the thermostat."
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  7. #7
    Join Date
    Apr 2009
    Location
    Conestoga, Pa, USA
    Posts
    199

    Default "Just an update. I was at the

    "Just an update. I was at the boat today and installed a thermostat. When I started the engine, my hot water heater hose (the one that connects to the bottom portion of the thermostat housing) threw water everywhere. The "plug" that the hose connects to was disolved. So I must get that "plug" and chisel it out and try some more. Will keep you all posted. Thanks again, Bob"

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