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  1. #1
    WaterDR's Avatar
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    Why does Yamaha NOT put a BOV on their machines?

    If a BOV is such a great idea and prevents clutch failures why didnít Yamaha include them? Just being cheap?

    For those who have installed, do they really prevent clutch problems?


  2. #2
    moparguy's Avatar
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    Quote Originally Posted by WaterDR View Post
    If a BOV is such a great idea and prevents clutch failures why didnít Yamaha include them? Just being cheap?

    For those who have installed, do they really prevent clutch problems?
    I think that answer is 3 fold;
    1. Cost
    2. Additional failure point
    3. Reduces opportunity to sell replacement clutches

    A Bov wont prevent a clutch from failing, however it will prolong the life of the clutch

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  4. #3
    fussy1's Avatar
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    Ive done 160hours now on original clutch. Stage one tune and no blow off valve.

  5. #4
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by fussy1 View Post
    Iíve done 160hours now on original clutch. Stage one tune and no blow off valve.
    We have two 2017 GP1800 SVHO with Stage 1 Plus 91 octane tunes, no blow off valves. We ride a mix of smooth and rough water, often at speed.

    At 222 running hours (this just happened last week) one of the SVHO clutches began to slip intermittently. It would provide expected boost up to about 2/3 throttle, anything above that the engine power would suddenly reduce the next time the clutch needed to activate going over a wave. The clutch would not reengage until I fully and rapidly backed off throttle, then reapply throttle.

    I replaced that factory original 222 hour clutch a few days ago with a new OEM Yamaha clutch and the engine is back to 100% power even across rough water.

    The removed clutch shows no external signs of significant wear or damage and the one way clutch still works as expected using finger force.

  6. #5
    I’ve never seen a good explanation for a BOV. My guess would be that the wear occurs when engine power is reapplied and the clutch has to grab again. If so, how would a BOV help?

  7. #6
    WaterDR's Avatar
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    Yea...I am not making too much sense of this either which I why I asked. A BOV costs about $400. Willing to bet Yamaha would be able to spend about $75 in added cost to add one to their machines. If it really made a difference in reduced warranty claims to off set that, they would be all over it. The failure rate is likely pretty low. And the issue with the clutches may or may not be solved with one, at least completely because owners who install them, do still have issues yet not always, when they have a BOV installed.

    i would like to believe that if one was needed Yamaha would have one, but I know too that’s not 100% accurate. Why I do know is this....those that sell them, say you need it. And those that have bought one, say the same, which is pretty much the same rule with anything else.

    Another issue would be how they are ridden. If the BOV is truly helpful, it would seem that it would help more in choppy rough water or basically anytime the machine leaves the water with the throttle pressed right?

    Anyway, I am still on the fence and not on the fence enough to install one.

  8. #7

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    Quote Originally Posted by WaterDR View Post
    Originally Posted by WaterDR
    A BOV costs about $400. Willing to bet Yamaha would be able to spend about $75 in added cost to add one to their machines. If it really made a difference in reduced warranty claims to off set that, they would be all over it.

    i would like to believe that if one was needed Yamaha would have one, but I know too that’s not 100% accurate. Why I do know is this....those that sell them, say you need it. And those that have bought one, say the same, which is pretty much the same rule with anything else.


    Anyway, I am still on the fence and not on the fence enough to install one.
    Following Quote is From The Thread
    No Fuel Filter.... Problems... Engine miss Firing, Stalling....
    02-14-2019,
    08:39 AM
    Quote Originally Posted by WaterDR View Post
    No filter needed. Just a separator.
    Following Quote is From The Thread
    No Fuel Filter.... Problems... Engine miss Firing, Stalling....
    02-14-2019,
    08:39 AM
    Quote Originally Posted by WaterDR View Post
    Originally Posted by WaterDR
    I am sure if Yamaha thought one was needed, it would have one.
    WaterDr , I`m not trying to be condescending to you. I once suggested to you that the fuel filter was needed and you said it was not needed or Yamaha would have one on their ski from the factory . Now you are maybe thinking of installing a BOV on you ski??? Why a BOV and not a fuel filter? Fuel filter $18.00 vs a BOV $400.00. You do not have a fuel filter or a BOV on your ski now. So whats your change in thought? I am just proving a point, that on our own dime $$ we have to rethink these skis. We do need to add things to the skis to improve them like BOV s, Fuel filters..... I think both are needed.

    Take Care
    C J
    Last edited by cjk6119; 03-09-2020 at 04:12 PM.

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  10. #8
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by PenSki View Post
    Iíve never seen a good explanation for a BOV.

    ... how would a BOV help?
    My understanding;

    The SVHO engine has an electronically controlled throttle in the air intake. The throttle valve is between the intercooler outlet and the intake manifold, downstream from the supercharger.

    The ECU controls the actual throttle valve on the engine. Your finger control on the handlebar just tells the ECU how much power you desire. The ECU decides how much power (and RPM) the engine will actually produce.

    When the jet pump comes out of the water, say going over a wave, or the jet pump cavitates during a hard sustained launch, the ECU needs to limit engine power to avoid over-revving the engine since the jet pump water load suddenly goes away.

    So while running at high speed and the hull (jet pump) bounces out of the water, the ECU will suddenly and rapidly close the throttle valve on the engine to avoid engine RPM going beyond redline. The engine and supercharger are still spinning very fast, but now there is nowhere for the highly compressed air coming out of the supercharger to go.

    The supercharger wheel is still trying to force the air to flow towards the engine but the engine is not accepting the flow (since the throttle is almost fully closed). So the compressed air pressure spikes upwards and tries to flow backwards through the supercharger. The supercharger does not like that. Compressor wheel surge and shudder can occur until the engine RPM declines or the engine throttle re-opens. The supercharger shaft, drive gears and the clutch itself all experience spikes in torsion and force.

    The sprag clutch is already engaged tightly and the air pressure spike exacerbates the force the locked up clutch must endure.

    A blow-off valve acts by releasing the highly compressed air from the supercharger output at the instant the engine throttle closes. That is why the BOV is controlled by a small hose connected to the intake manifold. The intake manifold pressure drops suddenly when the throttle plate slams closed and that pressure change opens the BOV. That whoosh sound from the BOV is the compressed air being released from the supercharger output.

    Since the BOV opens when the throttle valve on the engine suddenly closes the supercharger wheel is not forced to work against an extreme rise in back pressure. This lessens the stress forces on the sprag clutch and the entire supercharger driveline.

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  12. #9
    Click avatar for tech links/info K447's Avatar
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  14. #10
    Baja FZS's Avatar
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    225 hrs on my SHO with original 2011 clutch. BOV went on at 7hrs

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