Need advice on adjusting my water pressure in jet boat.
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Need advice on adjusting my water pressure in jet boat.

  1. #1
    Mikes1975StarbuckJetBoat
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    Default Need advice on adjusting my water pressure in jet boat.

    I rebuilt my big block Chevy over the winter, and recently fired it up at the lake and promptly blew my left head gasket.

    I just finished replacing the left head gasket and doing the re-assembly of the motor.

    I wanted to ask how far open my valve should be that comes from the Berkely Jet pump hose for the engine water intake.

    This used to be adjusted properly and someone I know came over to look at the baot and moved the valve for the engine water from the pump to the first "T". It appears he opened this all the way up.

    I have a 402 big block chevy motor bored 040 over with a Berkeley 12JC jet pump with Bassett over the transom water injected headers. I just put new water injector hardware onto the Basset exhaust pipes too as the old ones were leaking before the rebuild.

    I would prefer not to blow another head gasket, but don't want to overheat my new block either.

    Any good advice for adjusting these manual valves for the water pressure would be greatly appreciated.

    Mike in Missouri - pronounced...misery

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  3. #2
    Hoodys and swim trunks Elkidminoltu's Avatar
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    Default

    First off, is it a ball valve or a gate valve?

  4. #3
    Mikes1975StarbuckJetBoat
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    It's a gate valve, it looks like a water vavlve on the side of the house...sort of.

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  6. #4
    Hoodys and swim trunks Elkidminoltu's Avatar
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    Good, that style has the most control over the water pressure that enters the motor. Most guys crack it a little on initial fire-up on the trailer and then open it more as the motor warms up. Keep it on the trailer and let it warm up and keep turning the knob until you get it where you like it. If you have it full closed when you first start it, it won't hurt anything. You have about a minute window before you have to start worrying about hot spots forming in the chambers and head without water.

    When you say he moved the valve, it's still before the T correct, as in between the pump and T?

    Your setup looks like this too correct?
    http://www.performanceboats.com//showthread.php?t=39650

    It sounds like something may be routed incorrectly and could cause a blockage that would blow the gasket. Was there water coming from the exhaust on the left side while it was running?

  7. #5
    Mikes1975StarbuckJetBoat
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    Nothing has changed in the water routing, I left all the hoses and both gate valves in place when I pulled the engine out for a complete rebuild in the fall last year. Yes, the gate valve is before the T in the line. There is a 4000psi line coming from the jet pump that the gate valve then goes into the line and then the line continues to the first T.

    I have a gate valve on the right (starboard side of the boat) that limits how much water goes out the back of the transom. I don't believe he jacked with that one after I said something about touching the valve to the block fro the pump.

    When I changed out the head gasket on my fresh motor rebuild, I made sure to chase all the head bolt threads in the block to ensure I was getting an accurate torque on the head bolts. I used ARP bolts, and ARP bolt sealant. I wasn't sure if the machine shop had done this or not so to play it safe I cleaned all the threads before trying to put a new head gasket on the block. I also cleaned the left head, and the block surfaces with solvent followed by alcohol to ensure it was clean. After assembling the head and torqing the head bolts to 75 /65 for lower bolts I readjusted my valve lash cold on all my valves. Then installed the intake manifold, distributor, and all the water lines back onto the motor. I checked where the gate valve was currently, it appears to have been opened up all the way.

  8. #6
    Mikes1975StarbuckJetBoat
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    He did not move the physical location of the valve, he only turned the round handle, in case I did not make that clear.

  9. #7
    Senior Member 74glencoe's Avatar
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    I realize I am opening up a can of worms, but here it goes. I had water pressure issues, so i decided on a overpressure dump, Now I never go above 13 psi at wot, and I have about 4 psi at idle. I had a gate valve, (still have one now), but the dump line took out all the guess work. I also put a fuel pressure guage in the intake water crossover.
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    Boating is nothing like cocaine, boating is much more addictive and results in bigger parties!

  10. #8
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    youneed to go to the dump valve asap keep the gate directly after the pump)full open) in case of water line leak(you can shut off all water aNd not sink).otherwise youll not have much water runnin through the block.go with the dump and have the volume and the propper pressure so as to not put water through the gaskets or into the oil,also very bad,,,about 85 at mcmaster carr or grainger....mike

  11. #9
    Mikes1975StarbuckJetBoat
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    Thanks for all the replies you guy's, I appreciate it. Thinking seriously about installing a pressure relief system as mentioned in previous response. Looks like a simple solution to an age old issue. Thanks again!

  12. #10
    Junior Member
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    Default water pressure dump

    Mike's got it right old school used a water valve to control temp, but this also efects water volume. this is a pic of a control valve. my water pressure never goes over 12 psi with full volume to keep it cool. I'v heard it said that a good jet can generate 80 psi ==blown gaskets
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  13. #11
    The Man cordog009's Avatar
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    When I hooked up my pressure relief valve, I had a manifold inline that would allow me to hook up a water hose between the pump and motor. I could close off the line to the pump and I put AN caps on the thermostat outlets and had a pressure gauge mounted there as well, and turned on the water hose and set the pressure that way. I believe I had mine around 15psi before the relief valve would kick open. Cheap insurance and only cost me a few bucks.


    1984 Youngblood TX-19 SOLD

  14. #12
    I'm No Expert Shaun's Avatar
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    You want either a pressure regulator or a pressure relief valve. You can get a house regulator at lowes or homedepot, it's what alot of guys on use, including me. This topics been beaten to death, some guys say all you need is two dumps, some say adjust the gate/ball valve at the pump. Personally get the right tool for the job, a gate/ball valve was not designed to decrease pressure with out affecting flow.

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