Knocking noise at idle 2015 Mondo

Bought this boat at the end of last season. Only had a few outings last season. Didnt notice any unusual noises last year. First weekend out this weekend and noticed a knocking noise at idle. Didnt have alot of time to investigate since boat ramp was busy. Read about some people have issues with wakeplate rattling at idle? Any other ideas of what it maybe? Is there anyway to post a video which I took where you can hear the knocking, rattling, pinging noise? Engine is still under warranty but hopefully it's not a major issue.

You'll need to upload the video somewhere like YouTube, Vimeo, Facebook, etc and then link it here in order for us to see it. Have you tried holding the wake plate at idle to see if the noise stops?

I didnt know about the wakeplate issue when I was on the lake. I will try that 1st thing next time out. Here is a video with the knocking sound. I know it's not the best way to diagnose, but maybe someone is familiar with the issue.

Thanks in advance
Watch "2015 Moomba Mondo knocking noise while at idle" on YouTube
https://youtu.be/HhdtD_RotpM

Are you talking about that random "click/tap" sound every few seconds or so? I counted 8 times I heard it and all seemed to be intermittent and not in a set rhythm. Was that video on the trailer or in the water?

Yes..I counted 8 clicks / taps as well. Definitely intermittent. That video was with the boat in the water at idle.

My 16 does that never seem to bother me it’s nothing major if it’s intermittent I’ve got over 200 hours on it

I meant it's not a rhythmic noise, more random. I dont know if its intermittent or if its gonna happen everytime at idle. Need to troubleshoot next time out. ie wakeplate, in gear, different speeds,

I just talked to local dealer and he thinks it is part of the exhaust tapping on metal box in the back of the engine. He has seen 3 so far this season. He said it doesnt happen until the engine warms up and the pipe loosens and sags to tap on the metal box. He fixed the last one with a rubber hose and zip ties. He said the 1 he just fixed must have been doing it for some time because the paint was rubbing off black metal box. Gonna look this weekend at mine and will update.

Pic from above

Here is photo from dealer.https://uploads.tapatalk-cdn.com/201...15fe05bb49.jpg

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Interesting, a knock like that would probably be heard by the engine knock sensors and kill power too.

There has to be a better fix.


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Quote:

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Originally Posted by larry_arizona

Interesting, a knock like that would probably be heard by the engine knock sensors and kill power too.

There has to be a better fix.


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No..no...“Knock sensors” detect detonation which is a specific frequency. It will detect this frequency for a period of time and then reduce timing until it stops. As a FYI a internal combustion engine is most efficient and produces the most power right on the edge of knocking/detonation.

I wouldn’t call this a knock, I would call it a “tap”....metal tapping together...it’s something in the engine bay, NOT in the engine.

Quote:

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Originally Posted by brad460

No..no...“Knock sensors” detect detonation which is a specific frequency. It will detect this frequency for a period of time and then reduce timing until it stops. As a FYI a internal combustion engine is most efficient and produces the most power right on the edge of knocking/detonation.

I wouldn’t call this a knock, I would call it a “tap”....metal tapping together...it’s something in the engine bay, NOT in the engine.

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I am saying knock sensors will hear false knock and pull timing.

Exhaust rattle will get picked up as false knock. It can pick up noise anywhere in the engine bay. Knock sensors are microphones.

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Quote:

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Originally Posted by larry_arizona

I am saying knock sensors will hear false knock and pull timing.

Exhaust rattle will get picked up as false knock. It can pick up noise anywhere in the engine bay. Knock sensors are microphones.

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You’re right in that a sensor is like a microphone...however an engine and drivetrain will make all sorts of noise...knock sensors are designed to detect detonation frequency- not random tapping or other knocking type noises... For example, if you were to tap on the engine with a screw driver it’s not going to start retarding timing..

When you hook up hptuners you can see timing be pulled if the sensors hear anything that resembles knock.

I will admit I am not familiar with Ford , But GM sensors pull timing with sources of false knock, including tapping with a screw driver.

I wish the indmar ECM allowed use of HP tuners.


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My 16 mojo had a random knock that bothered me for the first season. Finally found out it was the plastic board that the ballast pumps are mounted too. Wedged a towel between it and the transom. Problem solved. Hope yours is an easy fix too.


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