Yamaha 60hp water pressure?

Discussion in 'Outboards' started by slow fred, Dec 29, 2011.

  1. slow fred
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    slow fred Junior Member

    What should the water pressue be on a 2008 Yamaha 70 HP, High Thrust at idle and 3000 rpm? Thanks.
     
  2. slow fred
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    slow fred Junior Member

    Are there any Yamaha dealers out there?
     
  3. marshmat
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    marshmat Senior Member

    I don't think I've ever seen someone measure the cooling water pressure on an outboard.

    Usually, we just look at it. If there's a strong, steady flow of warm water out the discharge hole at idle, the pump's good. If the flow's weak or intermittent, then the pump's shot, or a hose is loose, or debris is blocking the flow.

    Once it warms up and you give it some throttle, there should be water spraying out the exhaust (and the exhaust bypass ports, if it has them), and if that flow is missing, a thermostat might be jammed or a cooling channel plugged up.
     
  4. CDK
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    CDK retired engineer

    Yamaha isn't any different from other engine makers. Water pressure depends on rpm and condition of the water passages and is in fact totally irrelevant. There is no specific device in the engine controlling the pressure.

    As long as water flows from the discharge hole at idle speed, the cooling is OK. If you must open the throttle to see water coming out, install a new impeller.
     
  5. IMP-ish
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    IMP-ish powerboater

  6. CDK
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    CDK retired engineer

    No, they exist only to help you slim your wallet by $45.86.

    For inboard installations they may be useful, although a simple pressure switch and warning light will do better if you don't want to hang overboard to check the water coughed out through the exhaust.
     
  7. slow fred
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    slow fred Junior Member

    They also help when the outboard is mounted on the rear of a 40' houseboat.
     
  8. CDK
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    CDK retired engineer

    That is certainly true Fred, but also in that case a bright warning light is better than a gauge. You can even add a buzzer without extra wiring.
     
  9. slow fred
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    slow fred Junior Member

    It has the factory warning buzzer but, I was told that it has the new, high flow, low pressure, cooling system. It has a factory gauge also. At idle it shows 0 psi and a max of 6 psi, WOT. At idle, it is pissing a good stream and never has set off the warning buzzer. The dealer here doesn't have an answer. A new impeller didn't change it. Old impeller looked perfect. It is run in fresh water.
     
  10. powerabout
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    powerabout Senior Member

    Most larger outboards are pressure and temp controlled ( not sure on yours 2 stroke or 4 stroke?)
    The pressure at rpm is used to troubleshoot them so there will be a spec
    Thermostat stuck open at idle will result in low pressure more then likely
     
  11. powerabout
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    powerabout Senior Member

    HI CDK
    Where do you get a saltwater capable pressure switch?
    Cheers
     
  12. CDK
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    CDK retired engineer

    Any level switch for a dishwasher or washing machine will do.
    The switch body is plastic and contains a reinforced rubber diaphragm that even survives prolonged contact with hot water and aggressive detergents. Only the metal ring around the switch chamber needs protection against seawater.

    I use such a switch to warn me when there is less than 1/4 left in the water tank. Mounted low in the engine bay it gets the occasional shower from bilge water, so it looks terribly but still works after 10+ years.
     
  13. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    As a 0-15 psi gauge is usually what is recomended so that gives an idea of whats to be expected .....Quite a popular item in australia ..Its just a question of whats normal for your engine with everything good in good conditon .Any variation or gradual decline needs investigation . Saves that panic when a bit of shiiiit blocks the tell tail ( pisser for you yanks ) and saves getting a bad neck every 20 seconds ......

    Crazy isnt it ..you cannot put shiit but you can put pisser...
     

  14. powerabout
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    powerabout Senior Member

    Hi
    So with very small pressure it will close the contacts
    What is the water height that switches yours?
    Cheers
    Powerabout
     
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