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Are you as good as my mechanic?

Old 07-31-2019, 04:49 PM
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Default Are you as good as my mechanic?

The vessel:
2002 Tiara 3500 Open
Twin Crusader 8.1 MPI 485hp, 700 hours
Boat is very well-maintained, regularly serviced, etc.

The problem:
An intermittent knock or rattle below deck, coming from the engine compartment. Loudest on the starboard side, the banging usually happens when accelerating over 16-18 knots, almost always happens over 21 knots, and usually stops around 24-25 knots. I can sometimes get it to stop by just cruising or backing off the throttles.

Here are a couple of videos I shot that capture the sound. (Sorry for the poor camera work!)

Video 1 of 2

Video 2 of 2

The challenge:
My boat yard mechanic has located and solved the problem. Can you do the same, based on the information above?

For fun I'll send a $5.00 Amazon gift card by email to the first person who correctly diagnoses the issue. I'll check in every couple of hours to see if we have a winner and update the thread.

Good luck everyone!

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07-31-2019, 07:46 PM
tmd11111
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10 mm socket left in the hull.
Old 07-31-2019, 05:10 PM
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Motor mount attachment bolts lose. I saw the same thing on an older Tiara 31. The motor mounts were lag bolted down into the wooden core of the stringers. Not a good design.
Old 07-31-2019, 05:23 PM
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Loose shaft coupling
Old 07-31-2019, 05:29 PM
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did your keg come unstrapped?
Old 07-31-2019, 07:29 PM
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Originally Posted by hottoddie View Post
Motor mount attachment bolts lose. I saw the same thing on an older Tiara 31. The motor mounts were lag bolted down into the wooden core of the stringers. Not a good design.
Motor mounts were my first thought too, maybe a cracked mount that knocked when the engine was under a lot of torque, but no. The mounts, bolts, etc. are good.


Originally Posted by ReelNauti View Post
Loose shaft coupling
Good thought. I didn't come up with that one (though I did think that maybe something was loose around a stuffing box and knocking on a shaft). Again, no. Shaft couplings were good.


Originally Posted by streeter69 View Post
did your keg come unstrapped?
Now what kind of Captain would I be if I let something happen to the beer?! No, all adult beverages are safe and secure.


No winner yet. Keep at it everyone!
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Old 07-31-2019, 07:35 PM
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Hull flexing and taping stringer on the deck.

(Can't be too bad, you aren't bitching about it, so it has to be something stupid).
Old 07-31-2019, 07:37 PM
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Loose heat shield,

fire exintinguisher is rattling around.

Rattling hatch

Your wife is banging on the cabin door
Old 07-31-2019, 07:37 PM
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It doesn't sound engine related, however it is definitely metal on metal. It sounds eerily familiar to me. I would think engine to shaft coupling area and as mentioned probably a loose or cracked coupler. the sound is much akin to a worn out axle u joint in my opine.
Old 07-31-2019, 07:38 PM
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I’m going with something left in the bilge that shouldn’t be like a bucket or a loose hatch.

A loose plastic cup I left on the deck made a similar sound.

edit to say burford and I are apparently on the same page
Old 07-31-2019, 07:39 PM
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Prop retaining nut lose. Strut attachment bolts lose.
Old 07-31-2019, 07:43 PM
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Bent prop

anchor rattling

damn I want that gift card,

Through hull check valve fitting failed, ball and spring Type and underway at certain speeds the ball is bouncing off the housing
Old 07-31-2019, 07:46 PM
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10 mm socket left in the hull.
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Old 07-31-2019, 07:48 PM
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No hull flexing (would never happen with a Tiara).

Nothing foreign loose in bilge or engine room.

No hatches, covers, equipment or gear loose or banging.

Nothing from wife except her asking "When are You going to get that fixed?"

Prop & struts secure.

No bent prop, anchor is at bow and secure.
Old 07-31-2019, 07:48 PM
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Charcoal canister for the head came loose.

second guess is the tilt helm vibrating because you lost one of those rubber grommets.
Old 07-31-2019, 07:52 PM
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Morse code, from the guy cleaning the bottom of your hull
Old 07-31-2019, 07:52 PM
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Thru-hulls are in good working order.

Sockets are in tool box and secure.

Head charcoal filter was recently replaced, but is secure.

Tilt helm grommets are in place.
Old 07-31-2019, 07:56 PM
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Originally Posted by Burford1 View Post
Morse code, from the guy cleaning the bottom of your hull
He keeps falling off before I can decipher what he's saying!

Last time it was "Please help m___" but I didn't get the rest?
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Old 07-31-2019, 07:58 PM
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I'm gonna go out on a limb and say something is bouncing around somewhere
BTW . Did your mechanic diagnose it from a video or did he have the boat in the shop?

Just sayn
Old 07-31-2019, 07:59 PM
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Serpentine belt idler tensioner/pulley?
Old 07-31-2019, 08:06 PM
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I got nothing new to add. My brain is hurting.

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