Engine Clunk

[kylegansel]

Hi guys - I have a 2005 Malibu Response LX with an Indmar 320 LCR Engine. A few times over the summer and then yesterday we heard a clunk sound going from between idle to fast out of the hole. Some have mentioned a loose prop, loose pylon, and then failing drive damper. The prop is tight and the pylon is tight. My son actually caught the sound in this video.

My googling the forums though it sounds like a failing drive damper will have a rattling sound in the transmission at idle speed. I'm not hearing that and it my driver says it was clearly a "clunk" sound out of the engine box. I'm looking for direction here if anyone has any ideas. I've messaged my dealer also.

[MNshortliner]

How long do you put it in gear before “hitting it”? Seems you are going from neutral to hitting it hard with no delay to let the transmission get a chance to get into gear. I always drag my skier a few feet after they say they are ready then “hit it”

[kylegansel]

@MNshortliner We are putting the boat in gear before hitting it but maybe we need to let it sit a little longer. This same thing is happening to my neighbors '03 Response LXI very often. I failed to mention that.

[MNshortliner]

Can you post up a vid that shows what you are doing 5 seconds before you hit it.

[jimski]

@MNshortliner i had a friend who would drive my boat like that

Let’s just say he hasn’t dove my boat since

[kylegansel]

@MNshortliner here’s a bit before.

[MNshortliner]

It doesn’t seem you are hitting it to soon. About a normal pull up I would say. Have you checked the tranny fluid lately?

[kylegansel]

I did the annual change last weekend. I checked the fluid after and it was good. I’ll check again.

[2Valve]

I would have someone visually watching the tranny/shaft connection (under the hood) while someone else rotates the driveshaft from under the boat. My guess is that the connection isn't as tight as it should be.

[Wayne]

Add checking the motor mounts to your list.

 

As 2Valve mentioned. Open up the engine cover and repeat the maneuver with some one watching.

[kylegansel]

Just checked the tranny fluid and it’s fine. Just did a test drive and it ran fine. No clue....

[MNshortliner]

Maybe next time out hit reverse hard then go through a normal skier pull up scenario.

[rockdog]

You said you checked the pylon, but check it again, I had this happen in my SN some years back. Tighten it anyway..

[kurtis500]

(If it’s not something simple like a pole mount or rope tie down)

 

You need to check all the drivetrain components. This sounds like a bunch of things I’ve experienced in racing and recreational boating. Check your prop shaft couplers, the prop nut, tranny mount, strut and basically everything from the coupler out. Those clunks can be internal to a drivetrain component BUT if they are from the coupler down to the prop it can end badly if not found. Trust me.

 

Make sure the prop is not hitting the strut

Make sure the prop is forward on the shaft and NOT moving on the taper.

Make sure your prop shaft is TIGHT in the coupler to the tranny and not slamming forward when the prop applies force.

 

It’s very difficult to find running gear that is loose by hand. The slamming is done under high hp you can’t duplicate by hand. Look for wear, friction marks and similar.

 

I wouldn’t use it until found. Hopefully it’s in the tranny or just something loose.

 

It sounds like you have kids in the boat, make sure you find it. I put a boat on the bottom of the Parker Strip with my wife and 3 kids in it while I was skiing behind it because of a parts failure. (They were all fine, a fuel filter failed and caused a fire.. I sunk it intentionally. Still have it) You don’t want those memories.

[6balls]

That's not a backfire of some sort, folks? I'm no expert.

[powbmps]

My 03 RLXi was making a similar sound when "hitting it" to pull up a skier. It was a backfire in the intake. In my case, replacing the distributor cap seemed to be the solution.

[ReallyGottaSki]

Crossfire from moisture under the cap is common when the cooler nights set in like this. Sounded like a pop/fart in the intake

[A_B]

Does it clunk when you are not pulling a skier? You can rule out most of the other stuff if it only clunks when hooked to the pylon. Try a skier hooked to the rear lift ring if you have one. That would rule the pylon out.

 

It appeared to me that when the line became fully taught with load that is when the clunk sounded. My hunch is the pylon, and if it is tight, check what it is tightened to. I would do process of elimination above to help rule out stuff.

 

 

 

 

[DW]

Seems to have the intake pop sound to me at least from the video. I would expect driveline clunks to sound a bit deeper.

[eyepeeler]

It takes two people to check the tranny fluid properly otherwise your reading will be off and your tranny will be low on fluid.

[BraceMaker]

Had a V-Drive doing this and it was the shaft coupler at the transmission splined shaft instead of tapered and it was walking back and forth even with the nut tight. Sloppy fit between the splines and the coupler. Like said hard to find these by hand, I put a paint line across the nut, washer, coupler, and shaft as well as prop, propnut, and shaft. Then went out and full bore forwards and looked at it, full reverse and you could see the coupler shift out of line with the shaft.

 

I now use green bearing retaining loctite on any splined coupler that isn't meant to slide.

 

 

 

 

[markn]

Had a simliar sound in similar conditions on my 196. After replacing the transmission and still getting the same noise, I asked if they had checked the strut shaft bearing. Replaced bearing and all is fine....except I did not need a new tranny!

[kurtis500]

BTW, Im not too familiar with the underwater gear on that boat but in a typical V-drive a loose shaft that detaches can release from the coupler and slide out the back taking out the rudder. It will happen fast and the moment you release the throttle. Seen this in racing a few times and its why we run safety collar in front of the strut and log. Check to see if you have them and if they are at least tight.

[kylegansel]

Thanks for all the responses. I love this site. To confirm I do not have a v drive - it's a direct drive. So as I'm thinking through this I wanted to rule one thing out. On the Malibu Owners Facebook page I had quite a few guys say it's a failing drive damper plate in the tranny. I'm not getting that impression from the comments above. Is a tall tail sign of a failing plate a rattling sound in the transmission? That's a huge expense to have replaced so I'd like to rule that out.

 

Sounds like I need to:

 

1. Check the pylon. I guess I'll e-mail Malibu and find out what the torque should be. I'm relatively confident this isn't the issues as wouldn't the sound come from the pylon and not the engine box?

2. Change the cap and rotor. I changed it at 500 hours along with plugs and wires. The manual calls for this annually or every 100 hours I think. Most mechanics have told me "if it ain't broke don't fix it" when it comes to the cap and rotor but it's cheap to change it out. This sounds like it could cause the engine to backfire.

3. Check the strut bushings again along with the prop. I checked my prop a week ago because 3 weeks ago I had to install a new key. The old one was shot and the prop wasn't staying tight on the shaft. A week ago the prop was tight and the strut bearings looked fine. I didn't seem to have any play. The strut bearings were replaced 4 years ago when I got fishing line stuck in them. It ripped all the rubber right out so I do get under the boat and check on this.

4. Verify the coupler is tight to the back of the transmission and there is no forward play when torque is applied from the prop out of the hole.

 

Sound good?

[BraceMaker]

They both have couplers

[Bdecker]

Might try a little more trans fluid. Our response was super sensitive to being a little low on fluid. Almost as if the dipstick was intended to be read without screwing it in- threads resting on the hole. We were getting a clunk years ago after a dealer fluid change, added a little more and viola! I do not believe there is a risk in adding more fluid beyond it possibly venting into the bilge.

[kurtis500]

V-drive or direct, it doesnt matter. Similar thing from the tranny out. With an EFI/MPI motor Im not seeing how you get an intake backfire ONLY after a throttle hit and run normal otherwise. The electric/fuel control is pretty tight on those motors. Usually that issue is a carb tuning issue or intake valve problem. Can be broken cap or wires but it will usually present itself at other times.

 

"3. Check the strut bushings again along with the prop. I checked my prop a week ago because 3 weeks ago I had to install a new key. The old one was shot and the prop wasn't staying tight on the shaft. A week ago the prop was tight and the strut bearings looked fine. I didn't seem to have any play. The strut bearings were replaced 4 years ago when I got fishing line stuck in them. It ripped all the rubber right out so I do get under the boat and check on this. "

 

Just curious, did you install the key and prop on the taper properly? (Im not questioning your mechanical abilities) If the prop isnt fully forward on the shaft and the prop is hung up on the key it will move back and forth under power. Even if the nut is down tight on it. At high RPM it will shake badly since its mis-aligned. Best way to install the prop with a new key is to put the prop on the shaft/taper all the way forward and mark the location on the shaft and the distance to the strut. I torque the prop at this point. Then pull the prop and install the key. When you install the prop MAKE SURE the prop is in its marked position prior to installing the key, if its back any from the measurements the key is hangin up the prop on the taper. Torque the prop and always install a new nut....all of my propshafts are drilled for a pin to kep the nut from backing out. Slower direct or V-drives wont present this imbalance as much to the occupants but your strut bushings and etc. will go out sooner and you may bend the tail of the prop shaft.

 

[kylegansel]

@kurtis500 No offense taken. I'm a desk jockey but do a decent job mechanically. Learning more each year. Yes, when I "tightened the prop" and removed the key. I then put the prop up on the shaft and marked where it was. I then installed the key, push the prop on as far is it could go, and then used a new nut to tighten it up to it's mark. I may remove it again to play it safe just to check.

 

I'm still looking for an answer on the drive damper? Anyone, think I can rule that out?

[BraceMaker]

I’ve never had a drive damper give solid clunk noises. More of a rattle or grind. Usually also you can stick a magnet in the bell housing and dig for bits of spring (pull starter) if there is an opening at the bottom of the bell you may have loose bits in the bilge if it is failing. Might wanna grease that starter bendix anyhow.

[MNshortliner]

I broke a damper plate on my wake boat years ago. Did all the work myself and has been going strong since (another 150 hours or so). Not really hard just need to unbolt the tranny from engine, remove shaft coupler and tranny linkage, support engine and slide the two apart. My situation there was no warning signs. After it broke you could hear a little rattle noise when you put it in gear and tried to drive forward but not much. The welds on the splined collar broke free of the damper plate.

[MNshortliner]

I don’t think your situation involves the damper plate but not 100% sure.

Like I mentioned before, give it some power in reverse then hit it like you were pulling a skier and see if the clunk reoccurs.

[kurtis500]

good idea. Magnets in the bilge too.

[kylegansel]

@MNshortliner I actually did that quite a few times yesterday when I took her out for a test drive. I did not get any of those sounds. Put it in reverse (honestly needed to clean weeds) and then in drive and it was fine....

[kylegansel]

@BraceMaker So putting a big magnet on the bell housing I may catch a spring I assume?

[kurtis500]

So does it clunk each time you accelerate? most of the time?

[UWSkier]

Only test under load like with a skier?

[kylegansel]

@kurtis500 No - it only happened 3 times this summer I can recall including this past Saturday.

 

@UWSkier - Not with an adult. I have only testing with my son yesterday.

[BraceMaker]

@kylegansel not a big magnet just one of those autoparts stores magnets on a telescopic stick. If you dig around under the bell housing, pull the starter and dig around inside usually you will find bits of cracked off spring.

 

Of it the most common issues are either the springs start to break, the rivets snap (sometimes this means the whole thing goes ninja star and throws a chunk through the housing) or the central hub starts to slip/spin where its welded into the plate with the springs.

 

The whole part is there because the impulse from the engine is a tap tap tap tap tap, where as the prop is constantly loaded in the water. A V8 taps 8 times per 2 rotations, 1 cylinder briggs taps once per 2 rotations - the impulse of that tap tap tap must be transmitted into a loaded prop and the springs in the flex plate take up that impulse. Thats why I don't think one clunk sounds like a flex plate. Sounds more like a coupler slipping on its shaft or as mentioned something big like a pylon.

 

 

 

[skiinxs]

My bet is the coupler at the transmission end of the driveshaft. (as has been mentioned above a couple times). I'm not sure if Malibu uses double taper driveshafts, spline on the transmission end, or slide in coupler with key and square head bolts to hold. If it is a double taper, I would take the four bolts out to separate the driveshaft coupler from the transmission, slide it back and put a socket on the nut inside (just like on the prop end). See if it moves any when you re-torque it. You might be able to test this theory by running the boat first. Try taking off hard, then slowing down really gradually so the prop is always pushing, no water pulling it backwards from stopping. Hit it hard again and if there is no pop, you are definitely dealing with something loose in the drive train, most likely the coupler at the transmission end since you have already addressed the prop end.

[wilecoyote]

+1 on a taper being a possible cause. I actually lost a prop that way, first year I had the boat it would clunk and slip, then come tight. I thought it was the tranny and was going to get at it at the end of the season and then one day as my wife backed the throttle after dropping me at the dock the boat seemed to be in neutral no matter where the throttle was. Turns out the lock nut had spun off and when the load was off the prop it just went to the bottom of the lake. I can't speak to who if any of the manufacturers actually lap the tapers but if they aren't lapped they can come loose. On my boat there's only one taper (Supra Rider) and it's at the prop end. If anyone has pulled the coupler on the keyed type, it should be replaced, they wear and will be loose if put back on. if it's tapered, it should be lapped.

[kylegansel]

Hey, I'm back again. So this past weekend we skied and the boat ran fine. I checked the prop and it seemed fine. I pulled the boat to winterize it and was able to tighten the ski pylon more. I can't say the pylon itself was loose but I was able to wrench down the through bolt at the bottom of the pylon. I have a 2005 Response LX. I made the pylon as tight as possible. Is that okay or is there a torque spec I should be following? No transmission issues from what I can tell. I did put a tad more fluid in but that was it.

[MNshortliner]

It can’t really help you but my pylon moves and I looked to tighten it but it just goes through the floor then into a built in fiberglass “cup” and then one bolt through the cup and pylon. Not the best design I would say but is your pylon mounted and same way? Maybe I can get a pic this next week. It’s in a 2012 RCB.

[kylegansel]

@MNshortliner Yes - I believe mine is the same. It goes into some type of sleeve. I tightened it up. We'll see how she holds. I am going to inquire on a torque spec with Malibu on it also.