knocking sound

[deckwork]

We just took our craz out for the first time ever yesterday. We did not go on a water demo and this is the first tow boat we have ever been in. I noticed a rather loud constant knocking while boat it idling in water, very difficult to track he sound down to one paticular spot, I am quite sure it's not from engine. Dealer wants me to bring it in but trying to get input from other owners.
my thoughts are that it is either swim platform or trim trab/ wakeplate, but sound did not change when I stood on swim platform and when I got it home I was shaking trim tab and it seems to have a lot of play and could potentially create the knocking sound with the exaust being right there and potentially shaking it.

[mmandley]

Hard to diagnose a noise with out a video.

Does it only do it at idle?
Only at slow speed?
Still there when you speed up?
Does the sounds change as you speed up?
Is it a metal on metal knocking?
High pitched or lower pitched knocking?

If I was to completely guess I would assume something is lose and it's rattling but with out Haring it and a lot of details that's all it is, a guess.

Sorry to hear you have noises on your new ride.
I did get to water test mine but it was a few months before delivery.

Hope it works out as a simple fix

[Woody929]

I was in a mojo for a demo that had a knocking sound at idle... Turned out to be the Yeti Tumbler that was in one of the cup holders 😉

Maybe yours is just as simple

[deckwork]

Hard to diagnose a noise with out a video.

Does it only do it at idle?
Only at slow speed?
Still there when you speed up?
Does the sounds change as you speed up?
Is it a metal on metal knocking?
High pitched or lower pitched knocking?

If I was to completely guess I would assume something is lose and it's rattling but with out Haring it and a lot of details that's all it is, a guess.

Sorry to hear you have noises on your new ride.
I did get to water test mine but it was a few months before delivery.

Hope it works out as a simple fix

It's a low solid sounding knocking most noticeable at idle, started right away as soon as it was started still on trailer, did seem to change the sound when we adjusted trim tab at idle. Just wonding if other people's trim tabs rattle around a lot by hand the pin seems small diameter for holes.

[russellsmojo]

I was in a mojo for a demo that had a knocking sound at idle... Turned out to be the Yeti Tumbler that was in one of the cup holders 

Maybe yours is just as simple

If the yeti is rattling then it is not full enough!! JoBoo get me a refill!

[smileycvc]

Our craz has a knock as well. It does it in gear and at idle. The speed never changes. It knocks the same when running the wake plate. It's not the auto flow plates or swim deck.

My dealer came out and heard the knock but didn't seem too concerned. I have been trying to get into the dealer earlier than my scheduled June appointment to get this and a few other issues fixed but they are really dragging their feet.

I was going to pull my floor panels up and look around for anything obvious myself but almost all the bolts that hold the floor down are stripped on my boat. If you find out what it is please keep us updated.

[deckwork]

Our craz has a knock as well. It does it in gear and at idle. The speed never changes. It knocks the same when running the wake plate. It's not the auto flow plates or swim deck.

My dealer came out and heard the knock but didn't seem too concerned. I have been trying to get into the dealer earlier than my scheduled June appointment to get this and a few other issues fixed but they are really dragging their feet.

I was going to pull my floor panels up and look around for anything obvious myself but almost all the bolts that hold the floor down are stripped on my boat. If you find out what it is please keep us updated.


Will do

When I called my dealer he did not seem to concerned either wondering if it's a model problem

Can you narrow the sound down to an area?

The problem with mine is the knocking seems just as loud no matter where I am it's definitely echoing in hull, it seems just a little louder at swim platform.

Going to get a fake a lake and run it out of water to see if trim tab rattles at idle,

[Connolly_Crew]

It should be that the autoflow2 plates need a grommet. I know someone that bought the first Craz model in Alabama and he had the exact same issue. It was an easy fix for the dealer. SC knows about this but does not have the available parts to repair so they are doing it as the issue arises. Best of luck to you.


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[smileycvc]

Will do

When I called my dealer he did not seem to concerned either wondering if it's a model problem

Can you narrow the sound down to an area?

The problem with mine is the knocking seems just as loud no matter where I am it's definitely echoing in hull, it seems just a little louder at swim platform.

Going to get a fake a lake and run it out of water to see if trim tab rattles at idle,

No we haven't been able to narrow it down. It really echoes thoughout the hull. It sounds like it's rear of the drivers seat. That's why I wanted to pull the floor panels up.


It should be that the autoflow2 plates need a grommet. I know someone that bought the first Craz model in Alabama and he had the exact same issue. It was an easy fix for the dealer. SC knows about this but does not have the available parts to repair so they are doing it as the issue arises. Best of luck to you.


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I checked my plates after talking to you before. It's not the plates. I have gone to the back of the boat and held them in place and it still knocks.

[deckwork]

No we haven't been able to narrow it down. It really echoes thoughout the hull. It sounds like it's rear of the drivers seat. That's why I wanted to pull the floor panels up.



I checked my plates after talking to you before. It's not the plates. I have gone to the back of the boat and held them in place and it still knocks.

Yes ours sounds just like you are describing, did you by chance hold the trim tab/wakeplate? I tried to wrap tape around the pin but the pin is snug in the piston but loose in the bracket on plate holes

[smileycvc]

Yes ours sounds just like you are describing, did you by chance hold the trim tab/wakeplate? I tried to wrap tape around the pin but the pin is snug in the piston but loose in the bracket on plate holes

Yep it didn't make a difference for us. I held it from the water so I know I had a good grip on it.

[smileycvc]

I did some more searching around today with more people in the boat. I got in the water and played with the plates again. This time when I held the plate my passengers said the knocking stopped. I guess the guy I had in the boat before was wrong. It's a relief knowing nothing is damaged and I can check that off the list.

[deckwork]

I did some more searching around today with more people in the boat. I got in the water and played with the plates again. This time when I held the plate my passengers said the knocking stopped. I guess the guy I had in the boat before was wrong. It's a relief knowing nothing is damaged and I can check that off the list.

Thank you for the update. Just to confirm which plate is the cause surf tabs, wake plate or all. This really helps I did not want to take to dealer right away but was concerned it was a mechanical issue and did not want to continue using and make problem worse.

[smileycvc]

Thank you for the update. Just to confirm which plate is the cause surf tabs, wake plate or all. This really helps I did not want to take to dealer right away but was concerned it was a mechanical issue and did not want to continue using and make problem worse.

It's the center wake plate. The surf tabs don't seem to cause any noise.

[mattsask]

That's good news! I was checking mine today, wonder why there is so much play in all the tabs..

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[deckwork]

Got mine back in the water today, confirmed the knock was from wake plate took it to dealer they tried putting same bracket and pin on so I went around looking at other moomba to see what they had, to my surprise I found three different mounts.
U shaped bracket with long pin and three little black spacers per side. This is what mine had
u shaped bracket nut and bolt with one larger spacer each side this is what I had them put on, still need to test
two separate brackets with little pin and small spacers.

[CRAZy440]

Glad to here that someone confirmed the issue. Thanks! Mine does the same thing. SC will have to fix the issue with a retrofit upgrade. It is an annoyance but isn't a big deal. I was gonna call SC to get the retrofit if its is available and fix it later. The turbulence at idle speeds is just at the right distance that it is putting pressure on the wake plate to bang it up at down on the pin. Not much that can be done about the turbulence. Pin has to be tighter or a plastic bushing needs to be made to stop the metal on metal banging causing sound.

Crazy how sound travels. Sounds like the banging is behind the captains chair and its all the way outside the boat in the water! Sound is funny right? Physics rocks!

[deckwork]

OK got my Craz back in the water over the weekend and sadly the knocking is still there and I am really concerned that if it goes un fixed that it will only get worse because the bracket is aluminum which is a soft metal so the holes will only get larger as the vibration continues.

[k2davis1]

What was the fix for this? Mine started today 29 hours on boat

[deckwork]

What was the fix for this? Mine started today 29 hours on boatDid you confirm it is wake plate? I only managed to confirm it was plate by reaching under and holding plate with engine running.
We found the the sound really traveled, even noticed it when putting boat in water and I was in water taking bow hook off.
With bolt instead of pin it was not as noticeable but did not go away till I put fresh air exhaust on now the exhaust is not trapped between platform and plate.

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[k2davis1]

Haven’t been back in the water yet to test it out, will do in the next week or so. I have the FAE on mine already. When I first heard it I thought the motor was self destructing it sounds horrible but it goes away with load and rpm.

I had the boat in Lake Superior for 2 hours before it started. The only thing that was different than normal was the 55 deg water as I usually run on warmer inland lakes

We’ll see, thanks for your comments

[98outback]

My 2017 Mojo does the same.

[yooper]

Just found this!!! That knocking has driven me nuts from day one. Ordered my service kit today.