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Thread: Antifreeze in the engine bay

  1. #1
    Member TeXXaN's Avatar
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    Default Antifreeze in the engine bay

    I have a 1986 jetcraft with a 302 1991 Kem marine motor, ran good all day. The temp got to 210 while idling at the boat launch to load up, I noticed it so i back up and got water moving that dropped the temp alot back to 160, when we loaded the boat i went to clear the sand trap and pull the plug. There was a crap ton of anti freeze in the bottom of the boat, and very little in the over flow and in the heat exchanger, i checked the exchanger today and there were a few clogged holes but not more than 10. What else should i look for. how can this much antifreeze escape through the cap?
    Diamond Justice MO 70lbs
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  2. #2
    Member GrassLakeRon's Avatar
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    Every 302 I ever had loved eating head gaskets.

    one day closer to alaska.
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  3. #3
    Member TeXXaN's Avatar
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    Eating a head gasket means, milky oil and rich exhaust smell, this isnt happening here. It was in in the bottom of the boat. I checked the lines for cracks or plugs nothing.
    Diamond Justice MO 70lbs
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  4. #4

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    Quote Originally Posted by TeXXaN View Post
    Eating a head gasket means, milky oil and rich exhaust smell, this isnt happening here. It was in in the bottom of the boat. I checked the lines for cracks or plugs nothing.
    I was going to suggest checking all connections...freeze plugs, in particular, hoses, etc. Sounds like you already have. Could a stuck thermostat be the culprit? Maybe re check the overflow line and connections to be sure there is no obstruction????

  5. #5
    Member TeXXaN's Avatar
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    just got back from a boat test run at the lake got it temp then bounced back down, slight leak at the thermostat area, going to try and pull a 302 intake manifold and hopefully this fixes the issue. I love the boat, 302 v8 runing 32 river miles burns 13 gallons, and thats at 3400rpm at 26-28 mph. Pretty good burn rate I think. She is thirty years old and we named her the Silver Slut.
    Diamond Justice MO 70lbs
    Shut-up And Hunt

  6. #6
    Member DRIFTER_016's Avatar
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    I was going to suggest checking the water pump.
    Look at the under side of the pump, there is a hole that antifreeze will run out of if the pump seals are gone.
    It's directly behind the pulley 1/2 way to the back of the pump and is about 3/16" diameter.
    You can reach back there with your hand and feel if there is antifreeze leaking if you can't get a look in there.

  7. #7
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    I would not pull anything off until you determine where it is leaking. You should be able to see it if as bad as it sounds. Try cleaning up the area under the engine, then lay down some white absorbent pads. Now you should be able to get a good idea what area it is coming from. You may need to use a mirror. It this fails, you could get some florescent dye from a good auto parts store (NAPA). Dump it in the cooling system and start the engine. You will need a black light to see where the dye is leaking out of the engine. It kind of sounds like there may be a thermostat problem if the engine goes beyond about 160 and then drops down to normal. Is this boat new to you? Is it the first trip of the year? Possible a freeze plug is leaking ? Was the engine winterized properly? Could be something as simple as a hose too. Good luck

  8. #8

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    I am with DRIFTER You could have the high temp and a leak with a bad water pump. Also agree I would not start fixing anything until you find the problem.Unless you just like to do extra work that does not need to be done. Good Luck

  9. #9
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    I have similar age boat with the 302 in it. Very happy with its performance over the years. I did have the thermostat stick closed and cause it to over heat. The stem had worn through the cap part of the thermostat. Simple fix and problem solved. I'd diffentily replace yours if you haven't already, before pulling anything else apart.

  10. #10
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    I just had this problem. It turned out to be a crack in the hose from the heat exchanger to the overflow container.

  11. #11
    Member TeXXaN's Avatar
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    Helicoil will be going in the cracked thermostat housing mount hole. Hopefully that's fixes it.
    Diamond Justice MO 70lbs
    Shut-up And Hunt

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