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knocking when not under load


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My 2012 VTX has a Monsoon 350.  Intermittently, it has a knock when in neutral and when engaged in gear but at idle speed.  As soon as there's any load or higher than idle RPMs, the noise goes away.  Again, this doesn't happen all the time and I haven't been able to pinpoint the source location or the circumstances that cause it.

I've read the dampener plate threads and the circumstances don't seem to fit perfectly.  Anyone have an idea of cause or, more importantly at this point, whether continued use threatens a catastrophic failure (e.g., the dreaded dampener plate explosion)?

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3 minutes ago, bbelt said:

I have been noticing similar issue in my 03 response.  I thought it was possibly in need of valve adjustment.  MIne only does it when cold.

 

Where are coupler bolts?

Attached to the coupler (hopefully) :rofl:

 

The coupler is where the transmission connects to the prop shaft.  In the case of your RLX - pop the floor panel

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Is it a knock or more of a tapping?  What is your oil pressure look like at idle?  

@bbelt I doubt the valves need any adjustment but crazier things have happened. My experience with a sbc is that this particular issue tends to be a lifter problem like one or a few of them 

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My response had a knocking sound and after multiple trips to the dealer it was discovered that the engine was actual touching the hull and that would amplifly the engine noise. slight adjustment and the knock was gone.

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On 8/10/2018 at 5:24 PM, Creekrat said:

Is it a knock or more of a tapping?  What is your oil pressure look like at idle?  

Knocking.  Oil pressure is 30-45 PSI at idle, depending on engine temp.  60ish PSI at operating speed.

On 8/10/2018 at 5:24 PM, Creekrat said:

I doubt the valves need any adjustment but crazier things have happened. My experience with a sbc is that this particular issue tends to be a lifter problem like one or a few of them 

Would a valve/lifter issue be intermittent though?

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  • 2 weeks later...

My boat is at glass shop in utah right now getting jetski damage repair so unable to answer the previous questions.   I am pretty sure it is inside the motor since I only hear it during cold start up and idle for the first 5 minutes or so.  Then I wont hear it again for the rest of the day. 

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