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  1. #1
    Cliffy's Avatar
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    Overheating Question

    First off cracking site, im new to jet ski's as this will be my first one

    Ive been offered a Polaris 780 SLT for 400quid with a over heating issue

    It runs for 10mins and starts to over heat, the guy is aderment that the ski runs fine just overheats after 10mins, he said it turns over fine etc

    Ive searched on here and seen issues with sensors etc, my concern is if that it over heats after 10mins am i looking at a engine rebuild??

    Any suggestions would be great, many thanks
    Neil


  2. #2
    Moderator beerdart's Avatar
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    Welcome to the hulk..

    Check item #9 it is a small orifice with a screen.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    Check that none of the cooling hoses are kinked, or collapsed internally. Check that the hoses have not been incorrectly connected

    Remove the thermostat housing (item 23), and check that neither the pressure bypass plunger (20), nor the thermostat itself (21), are clogged or worn/damaged.

    Also check that the water inlet screen, which is inside the jet pump exit nozzle, is not clogged. There is a sturdy plastic tube that runs along the right side of the jet pump, running forward from the nozzle side to the pump base. Make sure it is not broken or damaged.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk.

    If it's been overheated a few times, there may be some internal damage. Possibly bearing, ring or piston.

    See if you can perform a compression test. Then remove all the sparkplugs and the black plastic cover at the back of the engine. Try turning the crank by hand, and see if it makes any noise. It should roll prestty easily. (some resistence from the flywheel magnets is normal)

  5. #5
    Cliffy's Avatar
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    cheers for the input guys

    Im picking the ski up on saturday fingers crossed its cool

    It does run rev etc, sounds healthy enough.

    It does seems a bit bunged up through out so a good clean and degunk checking the pipes etc

    fingers crossed

  6. #6
    dghal's Avatar
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    well post back and let us know your findings......

  7. #7
    bowsniper's Avatar
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    Ah!!! Another Individual caught with the polaris bug I see! Cmon In and ride! WELCOME!!!. This IS the site to ride,ask,have fun,learn and meet other polaris lovers.
    Read My Post, ---Thats hot! ---- I put a motor in and switched the cooling hoses around by accident. Opps. But it still runs. I caught it befor she blew up.
    Pretty much stuff your face in your ski for a long time and stare at stuff in there looking,seeing where everything is routed and check everything out real close. Is there water in the hull? possible leak from hoses? or loose clamps? or clogged screens? Pump inlet too ..like 447 said.
    Dont run it more that a min or two max if you know its over heating and thats IF its in the water. The water keeps the bearing in the impellor housing lubed. thats how they get cooled. otherwise on land I would say 20 seconds run time. then let it cool. never more than a min. Thats with no water hose attachment, otherwise.you could run it for a few mins on the hose I believe. Could another member chime in on this procedure please. Iv'e never done it myself. I believe you start the engine, turn on the hose, turn off the hose stop the engine... is that right guys? lol . There's a attachment for this procedure too. It's off the coolant rail.You would have to purchase that before this would work. Or else you could ingest water into the engine if you do it wrong and that would hydrolock the pistons and cause the crank to get out of index or bust the woodruff key or both.

    I would recommend a infra red heat led gauge for testing the temp of the clyinders. there cheap now a days.. and give instant temps checks. Then when you run it , you can SEE the temps rise. Is it overheating in 1 jug or all 3 getting hot? they should be warm, not burning hot. like 144 or so. not 200 like a car.if you touch 1 jug and its like holy smokes thats hot. got a problem there! lol with the gauge you could temp all three in 12 seconds to check which are running hot. If all, then a restriction in the system or its not connected or plugged or backwards or mis routed hosing or even missing.
    Maybe check out all the routing for your ski from the schematics available here. Really get into it and See what your ski is all about.. I did it for hours and has helped me tremendously along with everyone here helping. After a while working with it, not getting frustrated.---suppose to be fun so make it fun! it's not a job soooooo, dont sweat it, WE'' ll get er running! ----You'll say hey, these arent too hard to work on after all. Theres only so much hose and wire and thats it pretty much. Good Luck!

  8. #8
    Cliffy's Avatar
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    well ive removed the housing parts 21 and 22 arnt in the housing so im guessing someone else has had ago at it before

    the part numbered 20 was stuck in there with salt rocks holding it in place

    im guessing i need to order parts 21 and 22 before testing the ski on water

    any views?

    also i remove the large tank in the back corner of the hull and found it to be quite sludged up what can i do to rise it through??

    thanks
    Neil

  9. #9
    Hayabusa's Avatar
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    Quote Originally Posted by Cliffy View Post
    well ive removed the housing parts 21 and 22 arnt in the housing so im guessing someone else has had ago at it before

    the part numbered 20 was stuck in there with salt rocks holding it in place

    im guessing i need to order parts 21 and 22 before testing the ski on water

    any views?

    also i remove the large tank in the back corner of the hull and found it to be quite sludged up what can i do to rise it through??

    thanks
    Neil
    You really don't need parts #20,21 or 22. Leave them out, put it back together and give it a test run.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Make sure part #9's screen is clean, (you'll need to remove the fitting to inspect) and the orifice isn't blocked up.

    Be sure to check the hose fitting on the exh manifold is clear also.

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