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Thread: Regulating water pressure

  1. #1
    Big Inch
    The thread leading up to this one is here http://***boat.com/forums/showthread.php?t=160051 if you care to see what led up to this.
    Does anyone know if it is possible to reduce water flow or pressure on my boat. I have a Bravo one drive leading to a Mercruiser seawater pump and am looking for a way to reduce the water pressure to my motor so I can effectively increase my motor temperature. I tried running a t-stat but I need a better way. The motor runs better at higher temps but I'm afraid of creating too much pressure in the block/heads. I have a water pressure gauge and oil temp gauge on order. Regardless of what my pressure reads at rpm I still want to find a better way to raise my temps then using a t-stat and the only thing I can think of is finding a controlled way to reduce the water pressure or intake.
    Please help

  2. #2
    BrendellaJet
    this is what we use on jet boats...
    http://www.***boat.com/image_center/...igging_001.jpg
    You could also use a different volume of line for the exit water which would raise pressure(within safe limits) and increase temp also.

  3. #3
    BrendellaJet
    what block pressure are you using? What kind of head gasket? Im seeing 20-23 lbs of block pressure as read at the thermostat housing(cometic gasket). Again, this is on a jet boat but the engine doesn't know what its turning...

  4. #4
    Havasu Hangin'
    I don't believe lowering pressure will increase temps. Some pressure in the block is good- it lessens the chance of steam pockets.
    Maybe you want to reduce flow? To reduce flow, most I/O's are setup with a t-stat and recirc pump.
    However, almost all the high performance guys I know just run a bypass and keep it cold. My motor temps never even register on the guages...but they seem to be very happy.

  5. #5
    Big Inch
    You could also use a different volume of line for the exit water which would raise pressure(within safe limits) and increase temp also.
    I don't want to raise pressure by increasing the pressure at the exit line. This is essentially almost exactly what the thermostat is doing in my setup and is what I am trying to avoid.
    what block pressure are you using? What kind of head gasket? Im seeing 20-23 lbs of block pressure as read at the thermostat housing(cometic gasket). Again, this is on a jet boat but the engine doesn't know what its turning...
    I'm not sure yet of the pressure. I have a water pressure gauge on order but I probly won't have it before the weekend so won't be installed for a couple of weeks.I want to make sure it is under 25 psi. I honestly am not sure of what head gasket was put on the motor. It was just rebuilt and I have not gotten a spec sheet on the build yet.

  6. #6
    Big Inch
    I don't believe lowering pressure will increase temps. Some pressure in the block is good- it lessens the chance of steam pockets.
    Maybe you want to reduce flow? To reduce flow, most I/O's are setup with a t-stat and recirc pump.
    However, almost all the high performance guys I know just run a bypass and keep it cold. My motor temps never even register on the guages...but they seem to be very happy.
    You are correct I am not trying to find a method to lower pressure. I temporarily installed a t-stat to test the motor at higher temps but this runs the risk of creating dangerously high pressure in the block. I am looking for an alternative way to reduce the flow prior to the water entering the block as a way of raising my temps. I am also open to other suggestions that would raise my temps.
    Without the t-stat my motor is sluggish and overly rich to the point of fouling plugs and backfiring through the exhaust. When I raise the temp I get much better performance out of the motor and also raise the oil to proper operating temperatures.

  7. #7
    cfm
    With a cross over system, to increase water temps you want to restrict water after the engine - ie: at t-stat housing - with restrictors (those big washers with holes) or a t-stat itself.
    These may create more water psi than you want - therefore you have to check this. If you find the correct restrictor and it causes more psi than you want, then you need to run a psi regulator just before the restrictor or block that will dump the excess water over the transom.
    Some people successfully use threaded brass plumbing water psi regulators and many pony up and buy the cheap but of course expensive Mercury Racing water psi valve.
    I would start the cheap and easy way. Get a Moroso or other water restrictor kit. they are cheap and come with a handful of restrictors that vary in orifice size and fit where a t-stat would on intake manifold. Watch your temps and watch your water psi. If both are where you want with no more mods needed, then your all set. If either or both aren't where you want than it's time to run a t-stat with bypass and water psi valve.

  8. #8
    cfm
    this is what we use on jet boats...
    http://www.***boat.com/image_center/...igging_001.jpg
    You could also use a different volume of line for the exit water which would raise pressure(within safe limits) and increase temp also.
    Do you have a manufacturer name + part # for that ? Where to buy ? I'd like to check one out. Thanks.

  9. #9
    don johnson
    I have seen your previous threads and ask why you want to increase the water temps? I have had both Pfaff and Teague motors and they like to run them as cool as possible. I currently have twin 1,100 HP 572 CI blower motors and they run right at 95- 100 degrees....
    I suggest you consider a different approach. Look at the tune on the motor. Sounds like it is off. I have run many big HP, big inch N/A motors and when the tune is right they ran great at low water temps....

  10. #10
    ck7684
    You need to be sure the oil is heating up enough to boil out any moisture...

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