What is this noise

[lawton]

I figured this would get more views here than in the Yamaha section, so I thought I'd try it here. I have a 2003 yamaha vmax hpdi 200. The engine starts and runs great but has been making the noise present in the first video linked below for several months now. It only makes the noise when in gear, and goes away at higher rpms, and its performance has remained consistent throughout the year. The noise in the video is about as loud as it will get, but on occasions it is quieter. The second video linked below shows the engine at neutral idle, and the noise is not present. I know this type of engine only idles on 4 of 6 cylinders when in neutral, not sure if that has anything to do with the noise. My first thought was that it was some sort of internal engine noise, but I'm really hoping that's not the case. Any ideas on what it could be?

[Rip Bass]

HPDI’s do kill some cylinders at idle but don’t when in gear,it sound like something might be loose with the exhaust,like maybe the exhaust tuner in the mid section.

[Bandone]

sounds like a piston noise but you say performance is still good so I guess its possible a exhaust tuner but seeing as I have been thru 3 of those when I owned a yamaha it usually hurts performance and never made any noise like that, take the prop off and see if the inside is covered with metal shavings thats a definite sign of a burnt tuner. have you checked out the prop washer and hub, see if its grinding into the lower unit, they wear until the keep digging in deeper and deeper you would be able to see the damage

[lawton]

I just pulled the prop and didn't see any signs of damage or metal shavings. Guess it sounds like it's internal

[mrdeath]

My 08 200 HPDI was making a similar noise all summer this year. I'd call it a rattle. Only at low RPM, only in gear and ran fine otherwise. Last month, I took off one morning and ran about 1/4 mile and it lost power. Still ran, would start and idle fine, but noticeably less power when trying to get on plane. Compression check revealed 0 psi on the #1 cylinder. Ended up being the ring locator pin came out of the piston. Had Hydrotec rebuild it. It's done, but I haven't picked it up yet. Yours is a 2.6 liter I believe (mine is a 3.3), but if I were you, I'd do a compression check now and see where it's at.

[OK_BassBum]

Definitely sounds internal, something has come loose but hasn't givin out yet.
Do the compression test, look at the plugs when they come out. I hit a tree with
the prop running across lake fork. (95 225 Johnson) I definitely felt the bump, but the boat ran for
the remaining three days we were there. It started ticking and then fell apart 2 weekends after we
returned. It clipped a wrist pin on the #3 cyl. and took a while to wear till it failed. If you know a decent mechanic,
they can diagnose it. If you can catch it before it blows you can save some money and not end up buying a power head.
Some of the old farts I know would take a stethoscope and listen to the power head. Crazy I know, but I have seen it done
and even listened to one, but it was a old Johnson 90 hp.
Good Luck!

[McQuaig]

If it only makes the noise in gear between 500 and 1000rpm (is fine at idle and above 1000) or so are you sure it's not prop rattle/chatter? Maybe try another prop?

[wmitch2]

Defiantly sounds internal. I'd get it checked by a mechanic before I'd run it again. Sounds like a disaster waiting to happen !!!

[lawton]

When I pulled the prop off last night to check for signs of metal shavings, I noticed that the prop nut was completely loose. It just spun off without any effort. So I tightened it back down today. Plan on testing tomorrow. If the noise is still there, then it'll go to the shop. But I'm hoping it's just a loose prop nut.

[mrdeath]

If your prop nut was loose, your thrust washer is probably starting to wear like mentioned above. Better check that before running it much.

[Bandone]

If your prop nut was loose, your thrust washer is probably starting to wear like mentioned above. Better check that before running it much

yep, it will just keep wearing and eat its way into the bearing carrier and that shaving might also get into the prop seal, I'm gonna take a wild guess and bet thats your noise. tightening the prop nut does not fix the problem, theres a new and improved thrust washer to the tune of I think its over a hundo!!! sure does sound like a powerhead ready to blow, but I have never seen one last for long after it starts knocking