I hope someone here can help.......
Donzi 27 ZR with standard 496HO and Bravo 1X. Went out today and a bit of noise getting on the plane. Over 3,000 rpm she ran perfectly, sea was very calm. Came back down to idle and heard a clunking sound through the driveline below about 3,000 and all the way down to idle. Took off again (very brave or a bit stupid) and it was fine at speed but worse when I slowed down and particularly if I trimmed the leg or turned either way.

Ive never busted a drive and don't know what it sounds like but I'm surprised she runs nicely at speed. I baby the boat getting on the plane and it's only done 150 hours. Really have no clue so wild guessing....
Could it be upper gears?
Gimble bearing?
Drive coupler?

To make things worse, the hatch lift gave up today. It's an electrical problem so I've unscrewed the hatch from the lift rams (screws are on top of the hatch) lifted it manually while back in the marina. Makes the noises in neutral also but I didn't want to drive it anymore. If I had some ideas from OSO it makes diagnosis a lot easier with my local dealer.

I have a 10 sec video and the sound can be heard pretty clearly but I can't post videos.

Appreciate any help and suggestions, last time I had a mechanical issue the advice here was spot on.

Thanks,
RR

Everyone has a different way of describing sounds but when you say that you hear it more when turning or trimming the drive that's a classic example of what happens with a bad U joint .
If it is silent when the drive is trimmed level and dead straight then more than likely , that's what you're dealing with .

I once had a pretty bad alignment issue that made some bizarre and intermittent noises but that seems different than what you describe .

It's not misfiring is it? I've had several 496's in v drive applications rattle like hell at idle when they misfire.

Without more info I'm thinking gimbal ring and steering pin. See how much slop you have

I agree it's probably the input shaft joint if it's doing it all the way to 3000rpms. The only other bad noise they can make is when the rubber finally burns off the internal flappers or the shafts that hold them get a little loose. But that is usually heard at lower RPMs

Thanks for the input.

Left the boat in the water, marina staff will have pulled her out later and I can't get back there for a couple of days. I'll do some more checking when I can see it out of the water, check drive for excessive play and look for anything obvious.

Funny how this could just happen for no apparent reason. Last time she was used was about 8 weeks ago. An OSO member and his mate visited Thailand (great guys, had a few laughs) and we ran her for a while and everything was spot on, left her in A1 condition and now she's Kaput!

It does sound a bit like a misfire but it's not. When the hatch was opened back at the marina, the engine idled smoothly but the knocking was still coming through the driveline somewhere.

Should have bought outboards!!!!

RR

U-joint

Yes I would say u-joint as well. I had the same issue with my drive as you are describing and it was the u-joint. Hopefully you can get it fixed soon and be back boating.

I'll add another vote for U joint.

A system logical approach to help find the issue is - in order

Drain gear oil and inspect condition and drain plug magnet. Most people gear oil needs changing anyways

next pull outdrive off, inspect U joints and movement, engine alignment with the correct tool , material on the shaft splines and so on,

Next is run the engine with the drive off - did the noise go away ? one seperates systems in a boat to see where the problem is located? Also stick the alignment tool in the coupler and run the engine - then watch what kind of circle pattern rotation the alignment tool is making.

while the drive is off - always look for water in the bellows pleats and of course corrosion - corrosion should NOT be on anything including the U joints, next - inspect the gimbel bearing and its rotation. If its the greasable bearing --- grease then rotate every 1/4 turn with fingers ( grease at every 1/4 turn).