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  1. #1

    Cooling system inquiry

    I know that the colling water comes in via the pump, to the exhaust (T'd off), then to the heads, hits the thermostat valve, and then escapes out the hose that T's into the exhaust right at the end of the loop..... because that is the way it is designed and engineered....

    Can anyone verify what the results of removing the thermostat and rerouting the inlet and the return lines, so that the cooling system is circulating in reverse....

    I have an experienced mechanic who hooked the cooling system up backwards with no thermostat, and I caught the mistake, WHEN INSTALLING THE NEW REBUILD, and even after seeing the fiche parts drawings for the cooling system, the mechanic swears that the engineer has designed it backwards....

    I know, its the twilight zone out there sometimes....lol ... but hey, mistakes r made...

    Can anyone give me their technical description as to what they think would happen to the engine if ran this way for an extended period of time.... (say 5 hours, in 3 ride sessions)

    It ran for 5 hours this way, and then failed.... and I need someone to verify exactly how and why it failed as a result of the cooling water circulating through the exhaust and the heads backwards....

    the actual result (near as I can tell) turned out to be an externally cracked head that was spraying cooling water out of the head and into the engine compartment, while the jet ski was still running... until it just completely gave up (probably due to salt water all over the spark plug wires and other electrical components)

    Can anyone tie this all together for me.... so I understand it fully...


  2. #2
    Connecticut CrazyA's Avatar
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    Your mechanic is wrong, the engineers are right.

    By entering the exhaust pipe first, the pipe and manifold help "preheat" the water a touch so you're not just dumping "cold" water on the cylinder head domes constantly.

    By reversing the flow you run a greater risk of cold siezure, improper engine operating temp, and the formation of air pockets above your cylinder head domes.

    If you're head (or any other part) was "misting" or "spraying" water inside your engine bay, then there's a good chance your engine internals have been exposed to salt water via the flame arrestor.

    How did it finally go down? You noticed it and stopped, or it died? Can you get some pics?

    Anyhow, your mechanic is wrong.
    Hope this helps.

  3. #3
    Quote Originally Posted by CrazyA View Post
    Your mechanic is wrong, the engineers are right.

    By entering the exhaust pipe first, the pipe and manifold help "preheat" the water a touch so you're not just dumping "cold" water on the cylinder head domes constantly.

    By reversing the flow you run a greater risk of cold siezure, improper engine operating temp, and the formation of air pockets above your cylinder head domes.

    If you're head (or any other part) was "misting" or "spraying" water inside your engine bay, then there's a good chance your engine internals have been exposed to salt water via the flame arrestor.

    How did it finally go down? You noticed it and stopped, or it died? Can you get some pics?

    Anyhow, your mechanic is wrong.
    Hope this helps.
    I know the mechanic is wrong.... but I had employees on the unit at the time and not smart enough to recognize a problem, they started to lose power... they thought there was plastic/garbage in the impeller and reached inside to check... found nothing in the impeller, so started it back up and limped it back to the marina running, laboring before they finally got it to shore (instead of shutting it of and getting a tow, to the shore, before deciding to do an engine inspection). The initial engine inspection, on shore, it was spraying cooling water out of an external crack in the head, as soon as they started it up...

    Is this crack in the head coincidence? Or can this be a direct result of running the cooling system, circulating backwards???

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    What ski or engine are you asking about? Thanks

  5. #5
    Connecticut CrazyA's Avatar
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    Quote Originally Posted by xlint89 View Post
    What ski or engine are you asking about? Thanks
    Yea, I probably should have asked that too huh? I looked at his profile first and thought it said 700, 700, 900.... I now see that it says 700, 750, 900.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Crazy, if you read his other post, it's really strange....

    He's got a 700 in a SL 750 hull

    A 750 in a SLT 700 hull

    And a 900 in a SL 700 or something really odd like that....

    Yeah, I'm wondering which motor because if it's the Fuji, the head itself cracked or blew a gasket.

    If it's a domestic, then it was just a head cover that cracked, but you already knew that, didn't you????

  7. #7
    Quote Originally Posted by xlint89 View Post
    Crazy, if you read his other post, it's really strange....

    He's got a 700 in a SL 750 hull

    A 750 in a SLT 700 hull

    And a 900 in a SL 700 or something really odd like that....

    Yeah, I'm wondering which motor because if it's the Fuji, the head itself cracked or blew a gasket.

    If it's a domestic, then it was just a head cover that cracked, but you already knew that, didn't you????
    It was the domestic 700, and the crack was in the EXTERIOR WALL OF THE CYLINDER HOUSING, the crack was right along the weld seam, from the head cap to where the cylinder bolts to the crank case, and the crack was on the same side as the exhaust manifold bolts on.

    You guys seem iquite nterested in the engine/hull configurations that I put together... I have 4 polaris skis, here in the Philippines, and to keep them all running over the years, we have had to do some mix and matching to keep everything running as often as possiblr (they are rental units).

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