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  1. #1

    cooling a GPR in warm water/weather

    has anyone tried using duckbills,removing the syphon hose,dumping all three cylinders out the back and running a seperate hose with fresh cooler water from the pump back in through the syphon hole into the exhaust??? will there be(enough/too much) pressure for the pipe??? Do i need 2 hoses? my thoughts are to get the warm cylinder water out and use cooler water to cool the pipe causing less heat soak...haven't tried it yet cause lowell still has my cylinders since later december....any thoughts??? P.S. i run riva heads

  2. #2
    Hydrotoys's Avatar
    Join Date
    Jul 2005
    Mesa, AZ
    Just saw this while researching some cooling options.

    Interesting concept. I don't have any answers.

    On my triple pipes, I have tested back to back cool water versus head water in my pipes, and the hot water makes 50rpms every time. It's been this way for a couple of years now, with no broken pipes.

    I CAN tell you that these holes in the R/d head are 1/4" npt and are WAY, WAY, WAY, WAY, WAY less flow than the stock head, and may explain some other issues.

    I can't even use these heads unless I open them up to 1/2" npt, with 5/8" nipples, since I'm using triple cooling...

  3. #3
    philip_gpr's Avatar
    Join Date
    Dec 2005
    Getting more water to the head can't hurt.

    But I think for maximum peak HP it is better to use preheated water from the head for the exhaust.

  4. #4
    ABBOTT's Avatar
    Join Date
    Jul 2005
    Birmingham, AL / Lay Lake
    Quote Originally Posted by philip_gpr
    Getting more water to the head can't hurt.

    But I think for maximum peak HP it is better to use preheated water from the head for the exhaust.
    I would think that is correct. Seems that the pipe needs a certain "amount" of water and it needs to be "warm" water too. also, too much water could be worse than not enough IMO.

    Dual cooling to the cylinders is another topic where as it needs the lake water "temperature" to hit the walls and as it travels throughout - it quickly becomes hot before entering the pipe just above the 3-way maniforld. Remember that too much water pressure from dual cooling from the pump could be a headach if not done properly because you have a better chance of water intrusion (forced in by way of the gasket layers) and then you will be screwed.

    Is an interesting topic however-- and i would like to learn more on stuff like this.

  5. #5

    Join Date
    Jan 2006
    Texas City, Texas
    I was under the impression:

    that the water passing through the cylinder jackets and head was to come out of the pissers at about 110-120 degrees for best effeciency..... that there is such a thing as getting the cylinders to cold and that 110 was the cut off. We should increase the cooling until we get to the "magical" efficient number to what I believe is 110 degrees.

    by increasing the number of pissers (water dumps) there is less and less water to cool the pipe. Your pipe should automaticly get hotter due to this lack of cooling.

    A hotter pipe generates more rpms. Having a hot cat con generates a hotter pipe and more rmps than the "D" plate. We loose about 50 rpms when we use the "D" plate. This is the perfect explaination. Having more pissers mimics the cat con scenario.

    To summarize... increasing the pissers serves a dual purpose. Water volume to the cylinders increases to make up for the pressure loss. More volume = more cooling. Water loss to the pipe because it is diverted to the pissers will heat the pipe helping to generate rpms.

    Can someone confirm?

  6. #6
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas
    running a seperate hose with fresh cooler water from the pump back in through the syphon hole into the exhaust??? will there be(enough/too much) pressure for the pipe???
    Two years ago, I did this. It was too much water pressure. I kept blowing my rubber exhaust coupler boot. That was even with #2 & #3 being dumped overboard.

    I went back to (stock) single cooling supply and it has been more than adequate. I live on the gulf coast where water temps get pretty warm in the summer.

    A slightly hotter exhaust is a good thing to have as it allows the ultrasonic waves to travel faster, thus producing more RPM's.

    Also, keep in mind that too too hot of an exhaust can be a "variable" in promoting detonation.....and "other things" can fall into play and be associated too such as fuel mixture, backpressure ect.....

    If you plan to remove your factory bilge siphon for whatever reason, replace it with an electric bilge pump. i.e.) Rule 500.

  7. #7
    i warped my riva heads last summer running all three heads to the pipe with the cat in there....i went to a D plate and ran the rest of the summer...I kept having problem's with my pipe bolts and head bolts backing themselves off... Possibly too much water pressure??? i'm not sure i'm not technical enough to check PSI and water temp coming out of heads,pissers,pipes etc...All i know is i changed it this year after having the ski torn all the way down for hull trueing,cylinder porting,etc...I changed to dumping all 3 cylinders out the back thru half inch thru hull pissers (looks like a triple piper) did away with syphon and installed duck bills(it's an 04 so it has a bilge pump stock) ran a double hole plate from the pump strainer with new goes to the island hole shot kit thru a thru hole fitting drilled through the boat and sealed with 5200...and the other goes through the old syphon hole into the engine compartment up to the pipe with the other pipe hole being blocked off....i've picked up 30 RPM from doing it this way...grant it the testing wasn't done on the same day...I have had no water leaks,or head bolt or pipe bolt problems with them backing themselves off...i've checked the torque and they are all staying in my humble opinion this is the way to go....

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