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Knocking noise just started


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Hi All,  I was out surfing today and I was pulling a rider and I heard a knocking noise.   I thought it was the tower at first but I lifted the seat where transmission is and it sounded like it was coming from there.  I took the boat out of the water and the prop nut wasn't snug up against the prop and I removed it and the prop slid right off.  Put everything back together hoping that was it and the knock was still there.  I felt around and I noticed all 4 bolts for the drive shaft coupling were loose.  I tightened all 4 but I was afraid to test it out as the sound coming from the transmission just didn't sound right.  Are these bolts supposed to be loose?  Could I have thrown the shaft out of alignment but really tightening these bolts?  I am going to rev the boat in neutral to see if I am still getting this knocking noise but I am thinking it is coming from the transmission area.  Any advice would be greatly appreciated!  (boat specs are 2007 23 LSV 383 Hammerhead).

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Loose props and engine coupler bolts can make a pretty good knocking noise.  Make sure your prop key is still in good shape, your prop is tight, your coupler bolts are tight, and it might be time to check your engine alignment and the transmission and vdrive fluids.

  • Like 2
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Thank you for the advice.  I have done the majority of the preventive maintenance (oil,plugs,impeller,rotor,distrib,plug wires) I read on here with the exception of changing the fluids for  the v-drive and transmission.  I will do that before I test it out.  I also read on here some of the boats of this age had dampening plate issues.  I only have 250hrs but it seems it can it happen even at lower hours from what I have read.

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2 hours ago, riot138 said:

 I also read on here some of the boats of this age had dampening plate issues. 

That was a problem Indmar had a couple years before your boat was built.  Yours is probably ok. 

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I've yet to meet a bolt that was supposed to be loose. Lots of loose nuts out in the world today, tighten your bolts...

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I tightened everything up and unfortunately the knock is still there.  It is a constant raddle at idle then when adding throttle the raddle goes away completely and than randomly at around 2500rpm and up there is knock coming from the transmission area.  It happens randomly  like every 10 or so seconds, sometimes more and sometimes 2 or 3 in a row. I'll be taking it in.  The dilemma I am in is the local dealer is a mastercraft dealer (30mins away) or I would have to cross the border into michigan for a malibu dealer (1.5hrs) and deal with customs and the potholes of Detroit.

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What you described sound a lot like a damper drive plate issue.  If it we're my boat, I would take a chance and continue to run it until the end of the season.  Otherwise, if you take it in now, your season is probably over.  I would expect any good shop that works on inboards can change a damper plate, and they are readily available from many sources online.

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23 minutes ago, csleaver said:

What you described sound a lot like a damper drive plate issue.  If it we're my boat, I would take a chance and continue to run it until the end of the season.  Otherwise, if you take it in now, your season is probably over.  I would expect any good shop that works on inboards can change a damper plate, and they are readily available from many sources online.

i have to disagree that a noisy damper plate could be run till the end of the season.

there have been times when those noisy damper plates failed at speed and took the bell housing, wiring harness and caused other collateral damage, too.

there is the potential for serious personal injury.

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It is most likely the damper plate, but I'd be weary on running it that way. They can do some damage when they let go. A shop with an overhead crane can change them pretty quickly, it's just them having the time to do it right now.

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update:  I changed transmission and v-drive fluids and made sure all coupling bolts were tight.  I took the boat out with my dad and you could hear the raddling again.  It sounded more in the v-drive area.  I brought the boat up to 3000rpm and then added a little more throttle and the needle actually went down.  As I was telling my dad we were losing rpms there was a huge pop and my dad said he saw the water under the v-drive splash up (there was a little bit of water below the v-drive due to a pretty steady drip from the packing).  I thought for sure something came through the housing but I couldn't find anything and the fluid levels haven't changed.  Every time I check the dip sticks though there is pffft of air that comes out like the v-drive and transmission is pressurized.  I thought the breathers on the v-drive and transmission would let that air escape.  So the boat is now in my driveway and I am hoping some shop in the area has the time to work on this. 

The one positive is my wife said to me I would never land a flip or spin anymore because I was 15 years younger when I last had a boat and I am too old and out of shape to do that now and I landed a backroll the day before this debacle so at least I have a told you so in the books all though she has a told you so that the boat was going to be a money pit.

Edited by riot138
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Update: I brought the boat into Tommy's and they said the cap, rotor and fuel filter needed to be replaced.  I had my neighbor who is a mechanic replace all that 3 weeks ago so I'm thinking I must have gotten defective parts.  Must of been some kind of spark knock or something I was hearing.  I haven't tested the boat out myself so I am still a little skeptical but they assured me after they replaced those parts and water tested it that it was running perfectly fine and the raddle while just out of neutral (no wake speed) is normal. 

Edited by riot138
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Hopefully final update:  I picked up the boat from Tommy's of Detroit this morning and took it over to a local lake there and ran it.  The boat ran great.  I asked why parts only a month old would fail.  The answer was basically the parts I had were inferior to the parts they put on.  I used indmar oem parts from Bakes but who knows if it was the parts or maybe they weren't properly installed but the boat is running again and I am happy with that.  The main problem she said was the fuel pressure was dropping and they replaced the cap, rotor and fuel filter (all parts I replaced a month ago) and that fixed the problem.

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28 minutes ago, riot138 said:

Hopefully final update:  I picked up the boat from Tommy's of Detroit this morning and took it over to a local lake there and ran it.  The boat ran great.  I asked why parts only a month old would fail.  The answer was basically the parts I had were inferior to the parts they put on.  I used indmar oem parts from Bakes but who knows if it was the parts or maybe they weren't properly installed but the boat is running again and I am happy with that.  The main problem she said was the fuel pressure was dropping and they replaced the cap, rotor and fuel filter (all parts I replaced a month ago) and that fixed the problem.

Glad to hear of a fast, affordable solution !

Steve B.

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