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Old 09 July 2016, 13:58   #1
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Boost pressure mercruiser 1.7d

Hello guys.

My mercruiser 1.7dti has too high boost pressure under full load. The boost gauge says 1.4bar (20psi). according to manual it should be max 1.2bar (17). Is it possible to adjust the pressure with the waste gate rod? should there be a certain preload on the waste gate rod when connecting it to the waste gate valve?
Or maybe its getting too much diesel?

<thank you
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Old 09 July 2016, 14:09   #2
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Do you know the gauge is correct/ Nik
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Old 09 July 2016, 14:13   #3
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Havent checked it, but it is brand new electric/mechanical. Its connectied too the inlet manifold.
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Old 09 July 2016, 14:53   #4
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not much help but i'd make a water manometer about the height of your house 46 feet exactly and check the gauge. ok only joking!!! Convince yourself the gauge is correct and take it from there. Ive got a tiny tach which was set up for me a few years ago. I have a honda set of outboard gauges / rev counter and its consistently inconsistent. i'd have thought correcting the boost pressure is prob very easy. Nik
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Old 09 July 2016, 15:46   #5
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Wastegates are known to get stuck on that engine, maybe worth checking if it operates as it should. Not sure but think that if it's not opening enough the pressure gets higher than it should.
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Old 09 July 2016, 17:52   #6
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Easy to check the waste gate is stuck ( it probably is as it's a common problem)
Remove the two bolts holding the presure operated waste gate actuator and see if you can push/pull the operating leaver in the middle of the turbo that's connected to the waste gate flap
Some are siezed solid and require a new turbo but you can sometimes free them off by spraying with wd40 & carefully trying to tap/ pry the operating leaver untill it moves once it's moving you can usually work it untill it's free enough to operate
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Old 09 July 2016, 17:56   #7
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Don't be tempted to just keep running it as you will crack a piston if the waste gate is stuck
They usually go like f-- when the waste gate is stuck but only untill a piston let's go which is almost inevitable so it's important it's fixed
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Old 10 July 2016, 07:44   #8
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Seized wastegate. If you.ve a high pitch prop on and/or operate at high revs the engine will self destruct so get it looked at and hopefully it can be freed up or you may be replacing the turbo as it's built into the housing.
It might be possible to fit an external wastegate but there's not much pipe work around that rather compact turbo
Let us know how you get on
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Old 23 July 2016, 07:11   #9
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hello again, I have checked the waste gate flap, it is operating freely, so the waste gate is not stuck. I have checked the waste gate actuator with a pump too chech the opening preesure, the rod starts to push on the waste gate at 1,2bar, for the waste gate to be fully open it requires 2,3 bar. Its not the waste gate, I also belive the turbo boost pressure should be more than 1,4bar if the waste gate flap was stuck closed.
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Old 23 July 2016, 17:15   #10
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Sounds like it just needs adjusted there should be a threaded portion and lock nut in the rod try screwing it untill it's cracking sooner
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