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What is this strange noise

L

Lawton

New member
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. I know it's not prop rattle as I've run it without the prop and it still makes that noise. I was thinking maybe it was the clutch dogs rattling at low rpms maybe. Any ideas on what it could be?

https://m.youtube.com/watch?v=1sh-buqh4uo

https://m.youtube.com/watch?v=AVrYuYk4kiQ
 
Are you sure they idle on 4 of 6 cylinders ?-----Do a compression test on this motor.---Post your numbers.----It sounds $$ expensive to me.----Did this condition show up suddenly ?-----How did it run for you last month ?
 
Put the boat on the trailer and drop the lower unit. You can run it on the flush hose and see if the noise is still there... May be the mid shaft support bushing....

HPDI does drop two cylinders below 16-1800 rpm.
 
Compression is good, 115-120 on all cylinders. It's been making the noise for a while now, probably since may or June. The engine runs just as well as it did before it started making the noise. I will try and run it without the lower tomorrow
 
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