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  1. #1

    Question about engine cooling at idle

    It seems that my waterbox is overheating because its not getting water to it, i had the jetworks mod installed, i opened it up all the way to see if it would help but nothing, when i blow through it its not clogged. So i took the ski out and at idle i noticed that no water is coming through the cooling lines at idle, even at low speed, i took the hose off that comes from the pump and into the stinger and ran the ski, no water at all, is this normal? At higher speeds, water comes out of the sides of the ski, and i have not had it say it was overheating once...

  2. #2
    Also wanted to add after running the ski for 2-3 min at full rpm on the water, when i parked it the stinger pipe was hot to the touch, pretty much unbearable.. i don't recall this being normal ?

    If anyone can help out, its going to be very warm tomorrow, and i don't want to get stuck on the river :-/

  3. #3
    Mighty Mouse's Avatar
    Join Date
    Feb 2011
    Probably exhaust plugged up with sand. Need to check your exhaust and inlet piping for clogs.

  4. #4
    i blew through the pipe that connects to the pump where water pumps in, it seems clear, im not sure why at full speed it works great but at idle it does not pump any water out.. anyone have any suggestions

  5. #5

    Join Date
    Jan 2006
    Texas City, Texas
    Usually, and this is not always the case, people have routed the water directly from the pump to the JW valve. From the valve the water goes to the stinger tail which then flows to the water box to cool and help supply backpressure for the engine. This backpressure helps to scavange fuel that would be lost in the exhaust system. If you disconnet between the JW valve and the stinger pipe, rev then engine past 3500 rpms, the JW valve will open because the pump is generating enough pressure to get the valve to pop open..... i.e. the JW valve is a relief valve that opens at the pressure you manually set when you adjust the valve to operate at 3500 rpms. IF YOU DISCONNET THE LINE AND FIND THAT THE WATER DOES NOT FLOW AT 3000-3500 RPMS, TWIST THE VALVE TO ESTABLISH FLOW AT THOSE RPMS. The line that was installed on the JW system should be 3/8 inch

    If you do not, then it is a matter of time before you melt you rubber couplings in the exhaust system and possibly sink/flood your boat.

    The reason that you do not show flow on the pissers while ideling is for the same reason that the JW system does not allow water to flow at low rpms. There is not enough pressure on the system for water to flow. Once the engine revs and pressure is established in the pump, then everything works as designed.

  6. #6
    Thank you for the great explanation, that was my main concern is the water coming out the pisser at idle

  7. #7
    could you tell me if i take off this hose off the stinger, and run the jet ski with the hose off (the hose that runs to the pump for the engine cooling) should there be water coming through it at idle... because mine does not have water come through it, even when i rev it a little. im just afraid there is no water running through the exhaust system at lower rpms and i don't know how to test

  8. #8

    Join Date
    Jan 2006
    Texas City, Texas
    Think about it this way. If the engine is not running hard, then it is not generating a lot of heat and you would not need a lot of cooling anyway. What if you were riding in really cold water? At idle with to much cooling water, it would not operate in its optimum temperature range..... just like a car when it is started on a cold winter morning. Super cold water with really hot cylinders theoriticly could lead to 4 corner seizures. (That statement will flame some for sure.)

    When you start your engine in the water, there is always water going through your cylinder and exhaust pipe jackets assumeing no pluggage. At idle there is just enough to keep the engine and pipe warm.

    There is a hose coming off of you stinger where the stinger angles down towards the bottom of the hull. It would be directly below your right thigh if you were sitting on your seat. This is the "overflow" for the cooling system, and this overflow dumps out the back of the hull. (This is the water you see and the route the water takes when you put your boat on a water hose at the house.) The stinger jacket has small holes at the bottom of it that allows a small amount of the cooling water to pass through the water box to help cool the rubber couplers. These holes are not big enough to allow all the water that is used to cool the engine to get out when at high rpms. The stinger water jacket fills with water as a result and takes the path of least resistance... through this bypass or overflow out of the back of the hull.

    What if there is still to much water flowing and the hose is not big enough to handle it? That is where the pissers come in... even more water can be dumped over the sides.

    To test your cooling system, pull the hose off of the stinger (5/8th inch line), reattach another hose and have it hanging over the side. Crank up your engine on a water hose at the house or on the nearest body of water and watch the water flow. If you rev up the engine, the water flow will increase at your favorite riding hole, because the pump is increasing pressure and flow. At the house, you are giving it a fixed amount of water at low pressure, and the water would not increase.

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