Rattle at idle and slow speed

[Bagar55]

The site is awesome. I'm addicted and have learned so much about my boat already. I'm a proud owner of my first wake boat. 2006 21V. Maiden voyage over this past weekend. Little windy and the water was a little chilly but found some smooth water and was smiling from ear to ear all day. I have owned numerous outboards and I/O's so I know boats fairly well but the whole v-drive and inboard setup is totally new to me. I'm not sure what is normal and what isn't at this point so any help would be great.
I'm wondering about a rattling sound that seemed to develop after running around for about two hrs. Didn't notice it at first but it sounds to me like it isn't a normal thing. I wasn't riding or pulling anyone just took the boat out for a cruise to figure out how everything worked. I came in, shut it down and loaded up the gear to go ride. Idling back out I noticed a rattling? sound coming from what sounded like the fuel tank area. Kinda middle of the boat. Couldn't pin point exactly where it was coming from. Not in the engine compartment area. Doesn't sound like transmission area. It almost seemed like it got worse the lower I got on fuel. Sounds deep in the boat. Possibly driveshaft? Boat only has 129 hrs on it. I notice it at idle and very slow speed. Noticing it at idle leads me to believe it isnt a driveshaft thing. When driving it happens below 8-10 mph. As the rpms come up it smooths out and I think disappears. I'm not sure where to start looking or what to double check. Performance is great. Hole shot solid. Pulls awesome riding. Any ideas or anyone else have a similar situation.

[CornRickey]

check the strut bushing for slop. This is the piece that supports the drive shaft on the bottom of the boatt. If someone ran it in gear with it out of the water it wears the bushing allowing for lateral movement of the shaft within the bushing. Probably not it but worth a check. I would also check the under side of the boat. The fins, paddle wheel and water intake fittings for anything out of place.

[Bagar55]

Thanks for the reply. I checked the underside of the boat when I put it back on the trailer and nothing seemed out of place or loose. Fins where solid and all intakes and paddle wheel where good. It is a louder more pronounced rattle or vibration than an intake or paddle wheel could cause. I have to inspect the driveshaft more closely still. When inspecting should there be any play or movement. I would assume no but not positive. Will check the strut bushing and see if there is any movement. Is there anything under the floor that could be rattling or vibrating around the fuel tank area.

[CornRickey]

I guess all you could do it take a look.

[cadunkle]

Sounds like it could be the coupler/damper, maybe broken springs or just worn. Wouldn't think so on a 2006 with 129 hours though. Check strut bushings, should be no slack or slop. Failing that, examine the coupler at the vdrive flange for loose or missing bolts. Also check shaft, could be bent. Look for any signs of hitting something.

[jzelt]

Some things to check:
Do you fell anything in the steering wheel from it or just noise.
Check the alignment, rotate the shaft from the prop slowly and see if any wobble in the shaft as mentioned above.

We struck a rock last fall.
Bent three blades on the prop.
Had it repaired and ran the end of the year out with slight low end vibration.
This winter went thru above checks. Everything appeared good, so went to prop next.
After eliminating everything above, replaced the prop and no vibration since.

[CornRickey]

I thought my damper was going out on my 86 last year after I dewinterized it. My dad called and said that it was pinging/rattling at idle in gear and coming onto plane. I figured it was the springs rattling. Went out to the lake and checked everything over prior to ordering it and found I crossed one of my plug wires which caused a slight miss which caused the springs to rattle. I'm sure it will need it in a couple hundred hours or so but it fixed the problem that I actually created.

[Bagar55]

Haven't been back to my storage yet to look at prop more closely and inspect drive shaft underneath the hull. I did check the shaft coming out of the drive while at the lake. No play. Seemed solid inside the boat. Will have to look more closely at the connection to v-drive but it doesn't seem like its something that would be that close to the deck as I'm assuming that would sound. Nothing felt in the steering wheel. No vibration through the wheel at all. The inboard v-drive setup is new to me so I can't be sure how a drive shaft wobble would sound. Wouldn't a drive shaft issue get worse as the rpms are increased? I guess it could go either way. To me it sounds like it is more in the middle of the boat or in front of where the shaft enters the water. Seems like it is around the fuel take area. Possibly even towards the front of where the tank would sit. Almost like it is below the tank towards the front. I'm not sure what could be under that area that could cause the sound. Might have to pull the floor up just to see.
Thank you all for your help. This site is awesome. Can't believe that everyone would take their time to try and help a new supra owner.

[cadunkle]

Where is the fuel tank on your boat? Being a vdrive I'd assume it's a belly tank like where a ski locker would be in an I/O or below engine area in a direct drive. There should be nothing mechanical in that area to make noise on a vdrive as all your mechanicals are aft. If it has an in tank fuel pump that could be it, or a ballast pump maybe check valve. Those things wouldn't make a loud noise though, and wouldn't be dependent on lower RPM though. You could try a mechanics stethescope to try to isolate the noise, or if you can't find one a broom handle to your ear and touch it to various parts of engine/transmission/vdrive/hull.

[jeffreyk573]

Bagar,
I have that same rattle coming from my 24SSV. Sounds like its coming from the exact same spot even. I have looked for the source of that rattle multiple times. And it doesnt start until the boat has been running for a while. And it doesnt do it all the time. I finally just gave up, I can't see where its hurting anything. Just live with it.
Just like I learned to deal with what turned out to be prop cavitation when I'm making a right hand turn pulling six people on tubes! Just enjoy your boat

[Bagar55]

Thanks for all of the advice. I have been digging into the boat trying to find the source of the noise. Found water in the vdrive. Not the issue causing the noise but glad I caught it after only using the boat for 3hrs. Now how the water got in there is yet to be determined. I believe it was from deep water in the bilge, bilge pump wasn't working due to dead battery. I have to believe it was from when I first picked it up from the dealer and towed it home. BS that the battery was bad but not a big deal in the end. Purchased the boat used so I was prepared to find a few things not exactly right. No cracks in the housing but looks like water got in through top of drive. Fixed the issue changed the fluid.
I was able to find the source of the rattle / noise. Upon better inspection of prop I noticed that the blades were bent ever so slightly. Only noticeable from the back. Starting really looking at the strut. Strut has just a slight bend. Feeling the bottom of the strut I found a flat spot. Looks like I missed it as well as the dealer when I purchased it. Very hard to see. Started up the boat and put it in gear at idle just to check it quick. Noise very obvious. Every couple turns the drive shaft is barely pinging off the side of the strut. The dealer I purchased the boat through is awesome and is replacing the strut and prop at no charge. I guess the sound was traveling up through the drive shaft and sounded like it was coming from up near the fuel tank in the floor. Hope this helps anyone else that might be dealing with a similar weird noise. Very hard to find.

[CornRickey]

Being that the shaft is straight I would think the contact with the bent strut would be continous. If its hitting intermittently as the shaft it spinning would that mean shaft is bent?

[cadunkle]

Yes, shaft would likely be bent. Remove shaft and put it in a lathe or jig, check runout with dial indicator. Should be no more than a few thousandths.

[Bagar55]

Taking the boat in to have dealer replace the strut. I have mentioned the same thing to them and the shaft will be checked. Very well could have a slight bend. Thanks again for all of the advice.