Banging, clunking and thumping. Driveline problem 496/Bravo
 

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 :sport009:

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).

Consensus seems to be u-joint which from my understanding, is relatively straight forward. It's only been in the water 4 times since engine and drive were serviced so you can imagine why I'm surprised.
I think Bup's order of work sounds pretty solid, I'll take that in to the dealer when I get a chance next week. Getting them to do the work may take a little longer..........:(

All greatly appreciated, thank you.

RR

Invite some more OSO guys back they'll have that drive off and problem solved in 20 min👍

There's an open invite to any of you but if you bring your wives/girlfriends, they can be a bit of 'anchor' on the nightlife here. Seriously, happy to meet anyone coming my way, the last visitors had a good time.

RR

P.S. I hope you weren't asking me to pay for your flight..........Lol.

Any news on the problem?

Dealer is flat out at the moment so we've booked for Monday 4th at 9.am. I will be there watching over their shoulder and will report back. I'm feeling pretty confident the forum is right and hopefully won't cost me an arm and a leg........

It's a bit hard here sometimes, only one dealer (2 branches) and neither one are at the marina where the boat is. They've always been good to me, no charge for on site work but if they're overloaded, there's not much I can do. I'm tempted to buy a few tools and pull the leg off myself but regardless of what I find, I'll still end up waiting for the dealer to fix it anyway.

I will definitely update here when I know more.

RR

rak,
my advice would be to buy the service manuals for the engine and drive
even if you have no intention of performing any level of maintenance.
here's why,
the dealer / repair facility may reputable or may be the only one around for miles.
buy reading and familiarizing yourself with part names and what those parts look like
the flow charts and recognizing everything has a torque value and specific procedure

by understanding the basics of how the thing works your jaw should hit the ground when you hear the old
wobble shaft is out of magnetic deviation causing the flux capacitor to damage the pcu which led to a misfire
that wore out the u joints,gimbal bearing, and the injectors need re calibrating because of the magnetic deviation i mentioned earlier.

Remember, on a Bravo application, the "drive/input shaft" is spinning as soon as the engine is started. Your "clutch" is the top of the Bravo outdrive.
As such, if you hear the noise in neutral, it's usually within the U-joints OR the gimbal bearing. I bring this up, because if you have bad U-joints, but you still need to fire up the drive to flush the motor, you could exacerbate your problem, especially if the U-joint lets go. The gimbal bearing can make mild to moderate noise if it's going out too; and that's a wear item that does need replaced from time to time.

Also, since your drive/input shaft is rotating as soon as the engine is running, you can't have the drive trimmed up high. This is hell on the U-joints; and will prematurely wear them. Make certain that when you are flushing on the rack or the trailer, that the drive is trimmed down to neutral. Also, you can't trim your drive way up and put it in gear to idle through shallow areas; for the same reason. Not everyone realizes all of this, and they prematurely wear and/or destroy their U-joints. When a U-joint comes apart at speed, it can literally break the drive off the back of the boat; seen it happen.

All probably good advice but........

I'm too lazy to do homework
I'm too old to learn new tricks
It's too hot here to do hard work
And the big one............I can get all the answers I need right here on OSO. :D

RR

P.S. I think the dealer here is very fair with me. On my last boat with Verados, they replaced all three shipper shafts, two of the Johnson rods and a helium flux capacitor for under 2k and they cleaned up so well afterwards, I couldn't even tell they'd been near the boat. :rolleyes:

When repairing boats one has to become a detective. Alot of times a failed part or more was caused by something else not the part itself that failed. Yes parts do fail as well, but alot of times something else cause the failure. NOT SAYING the OP -- U joints are good here but a failed ujoint all by itself on a 10 / 12 year old - low hour boat is not common, unless self inflicked or water intrusion or something made it fail.

Also just adding my opinion here --- owning the manuals without the many special tools and quality general tools sometimes is not worth buying for a boat owner versus an experience trained real marine shop do the work. Good quality marine shops can easily have 250 K to 500 K in tools, special tools, manuals and training at their finger tips. I can easily see where rak rua is coming from letting a shop do the detective work. Good luck.

Will add some people can have a huge struggle man handling a Bravo especially a bravo III when reinstalling it. One of my customers is dealing with this as he thought pulling his bravo III and reinstalling was going to be a walk in the park man handling it ---- he ended up hurting his back really bad .

totally forgot the johnson rods

Johnson rods on a Mercury, who would of thought...

Ken

I’m in awe of the Cajones to power thru the clunking /thumping noise that started at low rpm. 😀

Sometimes it makes it easier to find in the end

must be a hell of a swimmer / no great white sharks

Damn auto spell, it should have read 'jonsson'........... :)

I did confess it was either a brave or stupid move!
When I first got her up on the plane, there was only a slight noise which disappeared completely once on the plane. I actually ran it all the way to wot 4,900 rpm's, for a couple of minutes and it sounded sweet. Backed her off and then getting back on the plane, I could hear the noise again, perhaps a little worse, so I headed home. She ran beautifully at 3500-4000. Just cruising, so I was on level trim and a straight line to the marina.

Approaching the marina, I slowed down and the noise was getting worse so I tied her up, scratched my head and called it a day. Aussies are good swimmers anyway but I my wallet may have needed a life jacket.

RR

Service guys arrived on time, checked oil.....OK, so it's off with the drive.......

Uni-joint and yoke appears OK but even I knew something was wrong when I saw these little round things lying on their backs inside, in a puddle of water......

Gimbal bearing has died due to a small split in the bellows. They're coming back later today with more tools to remove the gimbal bearing. Meanwhile, the drive is going back to their workshop to give it a thorough checking.

Im not overly impressed 'cos when they serviced everything a few months ago, I asked them to check anything that could be worn/damaged and that should include the bellows. Oh well, could be worse...... ;)

RR

Your coupler could be the worse for wear after that failure, make sure they check it carefully.

Dropped back this avo' and they have removed the remains of the old bearing. I haven't spoken to the technicians yet but it all looks pretty normal to me............ Thais tend to fix the immediate problem and not always investigate further and I don't know enough to argue about it. They said they doubt there's any further damage so I pretty much have to go with what they say. :silenced:

I felt like a marine proctologist taking graphic photos here.........

RR

P.S. Top right of the 2nd photo, is that a rusted bolt head or just some rusty water and grease?

WTH are those things in the puddle in the bellows that look like metal ball bearings and where did they come from ?

That's exactly what they are, ball bearings from the gimbal bearing......
Do you want some of them? Free to good home but you pay the shipping. :)

Make sure to look close at the coupler teeth, with bearing that far gone it may have damaged it

The splines look to be in very good shape on the engine coupler, Gimbal bearings can make a lot of nasty noises when they are worn, obviously yours was way beyond worn! I think that rusty thing is the end of one of the bolts that is coming from inside holding the transom plate on. Give it a brushing and put some grease on it. If you solve the bellows leak there shouldn't be any more water in there messing things up.

Also while you have the drive off check the block where the trim hoses attach and see if that is all in good shape, the mercathode wires can rot out and leak and make a mess in there.

If there is any black rubber dust around the inside transom assy, that would be a sign that the coupler was damaged. Probably not but worth checking. A boroscope would be very helpful. Most good mechanics have one. Even available on amazon for less than 15 bucks. great for finding stuff dropped in the bilge. https://www.amazon.com/MiluoTech-End...ords=borescope

BE CERTAIN that they check and correct engine alignment before they put that drive back on there. It's a bit hard to "check" the coupler, but ensuring engine alignment is going to be paramount, especially after your boat spent all that time on it's side on the trip over. I would be CERTAIN to make sure that all of the engine mounting points are sound, and all fasteners are tight. I have seen gimbal bearings go bad before making noise and the like, but I have NEVER seen one come apart.

Have the techs SHOW you their alignment tool and show you how they use it. If they can't do that, you need to find someone that HAS the tool, and knows what they are doing.

What's with all the CAPS!

Last sentence - water in the bellows. and the GB

Also I see lack of proper maintenance here (not dogging you but it is what it is ) and you need a engine coupler might be yes percent wise. . Merc alignment tool OEM only not ebay brands

You will be fine and a tad better off if they install the NON greasable gimbel bearing. But have to install the correct one.

Really U joints inspecting them externally is not a true test nor their movement being completely free with rotation.. The true test to inspect u joints is to pull off the end caps and look for scaring, Also this is called Brinelling --- meaning u joint needle marks appear on the surface of the cross - this alot of times is caused by torque and driveline angles that a marine outdrive goes thru. - over time this puts excessives loads on the u joint bearings and ends up leading to failure. BRINELLING and I used CAPS for that word, haha