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  1. #1

    What causes water flow in cooling of STX-15?

    STX-15F, 2006 used exclusively in Salt Water and flushed after each use for ocean rescue. 40 hours on it (very hard hours). Had catastophic overheat condition this spring which melted water box hoses and bilge vent hoses. (No, I was not operating it or I would not have ignored the alarms )

    Clogged water box with salt and crap as well as upper and lower fittings on the water box muffler. Replaced water box muff, fittings and checked all flow through the hoses and everything seem to flow fine under low pressure.

    Ski now overheats after 15-20 minutes of run time with extremely hot muffler box. I'm not getting the water flow that I should out of the tailpipe (compared to a 2008 and 2013 STX-15 under same water hose test conditions).

    I am assuming that the water flow (when in water) is generated through a venturi effect at the exhaust manifold where the two water lines connect. IS this a correct assumption???

    I have a service manual and can not find if there is a test for a negative pressure at the Exh. Man fittings to see if there is enough vacuum being pulled to suck the water through the cooling system.

    The reason that I am suspicious about the Exh Man is because when I replaced the Water box and short blue hose that connects it to the Exh Man, the end of the exh man was severly deteriorated by the salt to the point where the replacement rings had no real grooves to seat themselves in. The grooves were eaten away by salt.

    If there is a negative pressure (vacuum) check at these fittings, I'd be curious as to what the reading should be.

    I'm not the best pwc mechanic in the world but I'm the cheapest that our volunteer rescue squad can afford. Our dealer is 125 miles away.

    Any input?

    Many Thanks

  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
    Join Date
    Feb 2007
    Old Hickory,Tn
    Check the water intake on the pump....where the hose attach to it in the back of the ski on the top of the pump....sounds like it could be clogged....

  3. #3
    Thanks...but I have been through the entire cooling system starting with the intake. I pulled the pump housing off and checked the strainer. I have flowed water through all of the hoses and there doesn't appear to be any restrictions in the oil cooler or any where else. I am kinda stumped at this point. I thought that I would start with the question, "What causes the water to flow?" I appreciate the input.


  4. #4
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
    Join Date
    May 2008
    Have you checked the fitting under the intake manifold and the gasket that seals the 2 pieces of the exhaust manifold?


  5. #5
    Yes to the fitting under the intake manifold, no to the gasket. There are no water leaks or exhaust leaks that I can see. I had to remove the intake manifold to replace the starter and checked the cooler and pipe at that time.

    If the gasket can be a problem, does that mean the exhaust flow is responsible for the water flow? or is it the impeller which forces water through the strainer to the engine?

    Thanks for the response.

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