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a64pilot 12-04-2020 14:34

Flex Plate Failure
 
I have a rattling sound at idle in gear, to me it sounds like a clutch rattling, but of course we have no clutch, so I assume flex plate, which I assume has similar springs in it that a clutch does.
Couple of questions, how often do they fail to the point to where there is no drive?
Do they rattle awhile before they completely fail, and if so how long?
Iím at Normanís Cay, jumping to New Providence tomorrow, then Chub Cay after that, and then onto Lake Worth.
The last leg in particular there wonít be sailing winds, so I will need the motor but worry if Iíll have it.

I know flex plates can fail of course, but have no experience with one failing, so I donít know the frequency of such a thing or itís failure mode.

rbk 12-04-2020 15:00

Re: Flex Plate Failure
 
Depends on the plate. Good quality one will last, a cheap automotive one not so much. I would replace asap while you can, pretty easy and cheap as far as things go. Just did ours by myself, pulled a cheaper one out with loose rivets that rattled a lot at lower speeds. Not sure how long it would have lasted but it had been doing it for a few years, lots of play in the old one. It may have taken one quick shift coming into dock or pushing into a wave who knows but Iím glad itís done so I donít have to find out. Worst case it fails catastrophically when you need it most and gets chewed up in the flywheel and you bust teeth off or worse snap the crank. They are considered regular maintenance but I canít remember the recommended interval. You could even try and replace with a cheap auto one where you are and get a good one when closer to home. The cheap ones work, they just donít last as long.

Bill O 12-04-2020 15:07

Re: Flex Plate Failure
 
What engine and trans do you have?

Besides the rattling, is there any extra whirring on start up? Is the noise from the rear of your eng./trans? (if yes, probably flex plate)

Does the rattle or high pitch noise go away w/slight increase of engine rpm or a consistently increase w/the rpm? If the rattle keeps time w/an increase/decrease then its most likely a broken spring in the flex plate about to come loose or maybe already in the bell housing.

Bycrick 12-04-2020 15:09

Re: Flex Plate Failure
 
When I bought my boat, I brought in an engine surveyor. During the sea trial with the broker and owner, he told me that he "heard something." After we got back to the dock, he had me shift slowly from forward-neutral-reverse at idle. Iím half deaf, but he convinced the others that the damper plate was bad and that to fix it involved more work than just replacing the engine. In any event, when we got the old engine out and in the shop, we pulled off the transmission and v-drive to rebuild. As we slid it apart, we heard a clink as something hit the concrete floor. Upon looking, it was one of the damper plate springs. Several of the other springs were loose where the plates had rusted.

Since then, Iíve seen a damper plate on another engine where the rivets holding the drive shaft sleeve to the plate had broken, apparently by rusting.

a64pilot 12-04-2020 15:23

Re: Flex Plate Failure
 
Quote:

Originally Posted by Bill O (Post 3115372)
What engine and trans do you have?

Besides the rattling, is there any extra whirring on start up? Is the noise from the rear of your trans? (if yes, probably flex plate)

Does the rattle or high pitch noise go away w/slight increase of engine rpm or a consistently increase w/the rpm? If the rattle keeps time w/an increase/decrease then its most likely a broken spring in the flex plate about to come loose or maybe already in the bell housing.


Only thing I have noticed is the rattling, and it’s only when in gear, and only low RPM, it goes away pretty quickly, say 1,000 or so. I left Long Island thinking I would be unable to buy fuel and it was low winds, so I was motorsailing with my code zero at 1,000 RPM, which gave me 5 kts to conserve fuel.
I think that made it worse. Got to Staniel Cay to find that their fuel dock was open 7 days a week, even during the shut down.
Engine is a 1987 4JHE with I believe a KBW20 transmission, I changed tranny fluid yesterday when I changed oil and it came out looking just like brand new fluid with no odor, I change it at a 100 hr interval with engine oil, I don’t believe I have a transmission problem, it shifts crisply and always has.

I’ve not listened to see where the noise is coming from, Since I’ve noticed it, I try to not let it happen, so when I put it into gear now I quickly add throttle to get to say 1200 or so.

I have a lot of experience with auto clutches, and believe a dampener plate is nearly identical, I knew about the springs of course and do know about the rivets that hold the splined center to the plate, but didn’t think about them failing, never seen that in a car.

a64pilot 12-04-2020 15:30

Re: Flex Plate Failure
 
$100,000 question is, do you think it will get me home?
I assume at higher steady RPM of say 1500 to 1800 the springs are doing very little flexing, the engine impulses are quick enough to not be working them?
I believe that’s their job, to absorb or smooth out engine impulses and not transmit that shock to the drive train?

rslifkin 12-04-2020 15:52

Re: Flex Plate Failure
 
Higher RPM should be less harsh on the plate. Realistically, any time the winds are decent enough to sail (even if a bit more slowly than you'd like to be moving), shut the engine down and sail. Less operating hours will reduce the risk of a failure.

Bill O 12-04-2020 16:10

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115389)
$100,000 question is, do you think it will get me home?
I assume at higher steady RPM of say 1500 to 1800 the springs are doing very little flexing, the engine impulses are quick enough to not be working them?
I believe thatís their job, to absorb or smooth out engine impulses and not transmit that shock to the drive train?


Obviously not being there can't exactly tell what's going on, but it may be gear lash or something other than the plate if the sound goes away at an increased rpm.
Approx. 1700-1800 rpm seems reasonable (mid rpm for your motor) and should get you back.

a64pilot 12-04-2020 16:24

Re: Flex Plate Failure
 
So your saying if it’s the plate, the rattle stays at higher RPM?
It’s actually always had this sound, but really at the threshold of hearing, I’ve heard that on most of the boats I’ve been on, it does sort of sound like diesel clatter.
Just now it’s much more pronounced.

What I guess I’m after is hearing from people that our boat did that, did it for a long time, finally had it fixed, or what I don’t want to hear of course is our boat did that, then a day or two after it started there was this grinding sound and we lost all drive.
It could I guess even be the Autoprop, but it’s such a familiar sound from my auto mechanic days. Drag racing of course it wasn’t uncommon to bust clutch springs.
Even then I don’t remember one completely failing to work, just sounded like Hell so we would replace the clutch.

I do realize of course that if I don’t use the motor it will last longer :)

Today foolishly I was sailing downwind and traveling with another boat, and 1200 RPM and I was doing 8 kts.
I should have just sailed at 5 to 6 and let him go.

Pete7 12-04-2020 16:36

Re: Flex Plate Failure
 
Take a long screwdriver and use it like a stethoscope to see if you can pin down the location. A rattle could be something simple like a loose air filter so worth eliminating a noise from somewhere else.

Pete

rbk 12-04-2020 16:36

Re: Flex Plate Failure
 
All the torque transfers through the springs and rivets even at higher rpm, bashing into a good wave could push its limits. No one can tell if itís going to fail without opening it up. Ours went for a few years without issue but our rear main seal was leaking so it was getting a nice oil bath and the springs werenít rusted. Yours could be all cracked or completely fine. I suspect when you get around to pulling it you will look at it and say wow I canít believe it held up that long.

AndyEss 12-04-2020 16:37

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115416)
Today foolishly I was sailing downwind and traveling with another boat, and 1200 RPM and I was doing 8 kts.
I should have just sailed at 5 to 6 and let him go.

Címon, most of us buy boats to try to be young and kids again.

Bill O 12-04-2020 16:38

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115416)
So your saying if itís the plate, the rattle stays at higher RPM?

The "rattle" (from the trans) should increase/decrease w/the rpm. If it goes away, it may not be the plate.

a64pilot 12-04-2020 16:49

Re: Flex Plate Failure
 
Bill, If they are like clutch springs and I strongly suspect they are, they are the connection between two parts of the plate, all torture is transmitted through the springs.
The rattle occurs because when the engine is at low RPM, it’s actually jerking, not a smooth rotation, but actually many quick jerks.
If the engine RPM goes high enough it smooths out and the jerks are very much less apparent. It’s also why many engines will shake at idle, but visibly smooth out at high idle or higher.

That is why I’m thinking it’s the springs.

Pete, not being able to fix anything, I don’t want to make it make the noise why I try to pin it down, gut says get it through the RPM range where it makes the noise and do not stay in an RPM that it does.

rbk, I hope your right, I’ve taken car clutches apart that were like that, with broken springs in the bell housing and what ones were left were broken, but it still worked, just was noisy and on a car made the clutch jerky when you let it out.

There isn’t anything I can do unfortunately, pre COVID shut down days, I’d head over to Spanish Wells to R&B boatyard, but now I guess I’ll have to cross my fingers.

It doesn’t help at all that tomorrow is the 13th, and yes even though I believe myself to be intelligent, I am superstitious. At least it’s not Friday.

rbk 12-04-2020 16:55

Re: Flex Plate Failure
 
See if you can find a part number and cross reference it to automotive and see if you can source one locally as a spare or have one mailed enroute to pick up. Itís not something youíd want to replace mod crossing but something easily done at anchor. Iím reality you could have it replaced in a day with minimal tools. As you know once the springs go all torque goes to the rivets and flywheel, it may hold but without dampening all the torque transfers to the crank and tranny.

a64pilot 12-04-2020 17:48

Re: Flex Plate Failure
 
Yeah, once I get to Lake Worth that’s viable, but I’m pretty sure it would take a Yanmar part.
However where I’m at it’s not really an option, Maybe there will be a boat yard open in New Providence? I doubt it though, everything that’s not a gas station, medical or a food store is shut down here in the Bahama’s, nothing is open, and I don’t see end of that soon, but that’s a guess.
Plan is to sail when I can and motor when I can’t. My crossing window is this Wed thru Thurs, then it goes to North winds and waves in the Gulf Stream

Davo1404 12-04-2020 17:57

Re: Flex Plate Failure
 
1 Attachment(s)
Brand new one for a 2GM20F.



Attachment 212678

Wotname 12-04-2020 19:07

Re: Flex Plate Failure
 
@ a64pilot, do you have access to the service manual while on board?

If you are short on bandwidth, I can post the relevant pages from the my 4JH2 / KBW20 manual.

LeaseOnLife 12-04-2020 19:50

Re: Flex Plate Failure
 
1 Attachment(s)
We have almost the same engine/tranny here (4JH2-TE, KBW20). Do you have enough clearance between stuffing box and trans-coupler, to move the shaft enough back, to remove the transmission? I would say 3" would be good, 2" too tight. Then the removal of the transmission is not that hard, given decent access. From there you can check the damper plate for broken springs and rivets. It also gives you a chance to spin the freed shafts in the transmission, check for noises and axial&radial play.


Edit and correction: judging by my finger, 2" might be just enough to get the transmission shaft out of the damper plate.

Frankly 12-04-2020 20:55

Re: Flex Plate Failure
 
I would take a mask and check out the Auto Prop. Easy to check and replacing a blade a lot bigger $ than the Yanmar damper plate.


Frankly

a64pilot 13-04-2020 03:47

Re: Flex Plate Failure
 
Quote:

Originally Posted by LeaseOnLife (Post 3115531)
We have almost the same engine/tranny here (4JH2-TE, KBW20). Do you have enough clearance between stuffing box and trans-coupler, to move the shaft enough back, to remove the transmission? I would say 3" would be good, 2" too tight. Then the removal of the transmission is not that hard, given decent access. From there you can check the damper plate for broken springs and rivets. It also gives you a chance to spin the freed shafts in the transmission, check for noises and axial&radial play.

Plan is to limp it home and then replace it there.

Frank, I should have, but I’ll run it gently today and see how it goes, I do have a spare prop on board and an Autoprop puller, just don’t know if I have tools big enough for the prop nuts.
I guess a hammer and cold chisel if I don’t.

Edit and correction: judging by my finger, 2" might be just enough to get the transmission shaft out of the damper plate.

Maybe, I figure worst case I’ll have to remove the engine mount bolts and slide the engine forward, I didn’t know it was only a couple of inches required, I figured you would need at least six to get the shaft to clear the bell housing.
I assume transmission comes first then the bell housing and that they aren’t removed as a unit?

a64pilot 13-04-2020 03:52

Re: Flex Plate Failure
 
Quote:

Originally Posted by Wotname (Post 3115503)
@ a64pilot, do you have access to the service manual while on board?

If you are short on bandwidth, I can post the relevant pages from the my 4JH2 / KBW20 manual.

No, I donít not the transmission end, figured R&R would be straight forward.
Have good band width now, leave in an hour or so, assume I will in New Providence.

Davo1404 13-04-2020 03:53

Re: Flex Plate Failure
 
I no that on the 2gm,you only have to remove the gearbox to expose the thrust plate. Hopefully your bigger motor is the same.

Captain Bill 13-04-2020 04:59

Re: Flex Plate Failure
 
I had a problem with my SD60 sail drives at about 1200 hours that was covered under warranty. When they had the drives out they noted that the damper springs were already loose and rattling around in the damper. The mechanic said that the current versions of the damper plate were rated at 1500 hrs and recommended replacing them since the drives were out and he would only charge me for the new dampers and 1 hr labor since the engines were already off the drive. The springs on the new ones were nice and tight. I don't know how long the original ones were rated for but they had to be replaced to accommodate the SD60 drives when I replaced my SD40s. In the literature that came with the install kit for the SD60's it mentioned the "new" style damper that meant that Yanmar had now standardized their style of damper plate across their small diesel product line. Apparently some engines used a synthetic polymer instead of springs and some used spring type dampers. If you read the service manual on the sail drives you will see a lot of parts have a service life rating of 1500 hrs, so I'm not terribly surprised that the damper plate would also be rated at 1500 hrs. My original sd40s did not have springs and seemed to be doing fine when replaced at 3200 hrs. I've also been told that low rpms are harder on damper plated than high RPMs. Apparently the power pulses they are designed to smooth out are far enough apart at low RPMs that the springs have enough time to decompress between power pulses and therefore move a lot, thus wear a lot. At high rpms the springs don't have enough time and essentially pretty much stay compressed. No movement, no wear.

rbk 13-04-2020 06:31

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115655)
Maybe, I figure worst case Iíll have to remove the engine mount bolts and slide the engine forward, I didnít know it was only a couple of inches required, I figured you would need at least six to get the shaft to clear the bell housing.
I assume transmission comes first then the bell housing and that they arenít removed as a unit?

Just the tranny, bell housing can stay in place. You may be able to leave your engine in place if you have the room and can slide your shaft back a few inches.

FPNC 13-04-2020 06:51

Re: Flex Plate Failure
 
Drive plates are a wear item. There is a good chance that they will not last the life of the engine.

Some drive plates are designed to provide a 'weak link' that will fail in lieu of one of the more expensive drive components failing should the shaft overload from say a line wrapping around the propeller and suddenly stopping the shaft from turning.

The spring type drive plates are notorious for becoming very noisy prior to failure.

Anyone considering sailing to very remote areas should be proactive and identify the particular drive plate that is on their engine and possibly any alternative vendors. This will give you the ability to source one more easily or better yet, keep a spare plate or elements on board in case of failure.

Frankly 13-04-2020 06:59

Re: Flex Plate Failure
 
Because of the much larger mass/inertia of that AP, not hard to imagine that damper plate takes a licking shifting into gear. That would be a the top of my list of suspects. But you are not in much of a position to do anything about that.

Lot of moving parts in that AP and loosing/ damaging a blade is a pretty big financial hit. Bahamas water might still be a little cool but it is pretty deep in the Florida Straights to try to find a missing blade. I change mine out in the water every year (dockside). If you happen to go that route just be sure to have a line on that prop. You ain't going anywhere but to the bottom when that prop comes off that shaft :facepalm:


Frankly

LeaseOnLife 13-04-2020 07:18

Re: Flex Plate Failure
 
2 Attachment(s)
Quote:

Originally Posted by a64pilot (Post 3115655)
Maybe, I figure worst case I’ll have to remove the engine mount bolts and slide the engine forward, I didn’t know it was only a couple of inches required, I figured you would need at least six to get the shaft to clear the bell housing.
I assume transmission comes first then the bell housing and that they aren’t removed as a unit?


The bell housing stays with the engine, together with the aft motor mounts, that would avoid re-aligning the engine, if you have the space. 10 bolts hold the trans to the bell housing. Not hard for a motorhead! :biggrin:


Pics shows tranny removed. You likely will see some loose springs in the damper plate, hopefully nothing broken. You can't do much about it but explain the noise and give you confidence to cross the stream.

Captain Bill 13-04-2020 13:24

Re: Flex Plate Failure
 
On my engine (sail drive so may not apply to OP) the transmission end of the bell housing opening is definitely not big enough to pass the damper through. The bell housing must be removed from the engine to mount the damper. Mine is a 3jh3 which is pretty much like the 4jh series except for the extra piston. Definitely check the size of the opening at the transmission end of the bell housing. It only requires about 2 inches of space to clear the shaft but I need an extra inch or so just to have some working room. If you can get the transmission out of the way with 2 inches of clearance, you're good. Given my sail drives I can do it in the water, but I have to move the engine forward about 4 inches to take the bell housing completely off. I can't move the transmission back, but then again I don't have to re-align the engine when I put it back together.

CassidyNZ 13-04-2020 13:42

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115436)
Bill, If they are like clutch springs and I strongly suspect they are, they are the connection between two parts of the plate, all torture is transmitted through the springs.
The rattle occurs because when the engine is at low RPM, itís actually jerking, not a smooth rotation, but actually many quick jerks.
If the engine RPM goes high enough it smooths out and the jerks are very much less apparent. Itís also why many engines will shake at idle, but visibly smooth out at high idle or higher.

That is why Iím thinking itís the springs.

Almost certainly the springs. And youíre right on the money with vibration at idle, many diesels do that and the springs in the drive plate will chatter accordingly.

Unless a spring breaks there is no failure issue and these springs can go on literally for years without breaking. As an example, my pick-up truck has loose springs in the drive (clutch) plate that chatter loudly when running against compression (down hill) and have been doing that for years, perhaps 50,000 kms.

Motoring your boat at constant RPM will not precipitate a failure, IMO.

CassidyNZ 13-04-2020 13:49

Re: Flex Plate Failure
 
Quote:

Originally Posted by a64pilot (Post 3115655)
Maybe, I figure worst case Iíll have to remove the engine mount bolts and slide the engine forward, I didnít know it was only a couple of inches required, I figured you would need at least six to get the shaft to clear the bell housing.
I assume transmission comes first then the bell housing and that they arenít removed as a unit?

Unfortunately on these engines, the bell housing forms part of the back of the engine and also provides part of the surface onto which the sump bolts. So the sump has to come off as well as the bell housing. Whilst it is possible to get the bell housing off without removing the sump, getting it back on is really difficult because of the sump gasket sitting on the bottom face of the bell housing.

Iím having trouble describing this accurately but I have done this job and tried unsuccessfully to ďpatchĒ in a piece of sump gasket, resulted in a bad oil leak. Not easy to get it right.

CassidyNZ 13-04-2020 13:59

Re: Flex Plate Failure
 
1 Attachment(s)
This is my bell housing picture from another thread. The gasket face is up against the engine. The red arrows are pointing at the face that makes up part of the sump gasket mounting surface. The green arrows point to the spot where the bell housing gasket and the sump gasket share a joint.

Getting these gaskets to play nice without removing the sump is really quite hard because the bell housing goes on with two locating dowels and has to be slid on horizontally thus dragging the sump gasket along with it.

Hope this makes sense,

Edit: And you’re correct, the transmission is removed before the bell housing. Working with the bellhousing while the transmission is still attached would be nigh impossible.

CassidyNZ 14-04-2020 12:52

Re: Flex Plate Failure
 
Quote:

Originally Posted by CassidyNZ (Post 3116128)
Unfortunately on these engines, the bell housing forms part of the back of the engine and also provides part of the surface onto which the sump bolts. So the sump has to come off as well as the bell housing. Whilst it is possible to get the bell housing off without removing the sump, getting it back on is really difficult because of the sump gasket sitting on the bottom face of the bell housing.

Iím having trouble describing this accurately but I have done this job and tried unsuccessfully to ďpatchĒ in a piece of sump gasket, resulted in a bad oil leak. Not easy to get it right.

Edit: this is not correct, just realised, Iím one step further into the engine than you need to be. Apologies.

a64pilot 16-04-2020 09:41

Re: Flex Plate Failure
 
No problem
So the sump doesn’t need to come off to remove the bell housing?

a64pilot 16-04-2020 09:47

Re: Flex Plate Failure
 
Anyway an update to what I feel pretty certain my problem is, cause I hate it when people don’t come back and let us know what the problem turned out to be.
It’s the prop, 99% sure of it. We are back in Lake Worth now and the prop made it. In fact it doesn’t rattle in idle either, but then I don’t idle in gear now, cause why push it.
It’s beyond overhaul apparently, but I swear at mid RPM, 1500 it doesn’t vibrate or make any noise, at 1800 it does rumble, but you have to put your ear to the hull to hear it.

Apparently 8kts plus and an engine speed of 1200 put so much pitch into the prop that with its worn bearings that allowed or made it make a rattle noise.

I don’t believe it’s the drive plate as the noise has disappeared, and I don’t think a plate would do that.

rbk 16-04-2020 10:08

Re: Flex Plate Failure
 
:thumb: thanks for the follow up. Good to hear you made it.

CassidyNZ 16-04-2020 13:34

Re: Flex Plate Failure
 
Well, that’s surely a whole lot less work. Good news. Although a new prop is probably a little more costly than a new flex plate.
:smile:

Oh, and no, the sump doesn’t come off to remove the bell housing. The bit that is influenced by the sump is the flywheel housing onto which the bellhousing faces.

Davo1404 16-04-2020 13:58

Re: Flex Plate Failure
 
Good news. More expensive, but an easier job

a64pilot 16-04-2020 13:59

Re: Flex Plate Failure
 
It only needs an overhaul. But being an Autoprop I believe the bits to do so cost more than say a new Campbell Sailor, which will never wear out, so I’ll be doing some thinking.

Frankly 16-04-2020 14:56

Re: Flex Plate Failure
 
I had a Campbell Sailor on my previous sailboat (Hunter 30). A good replacement for the factory 2 blade but not close to an AP.

New bearings on my old water lubed AP less than $300 and not hard to change. If the races need remachining then about a grand with two way shipping back to the factory.

IMO the AP is a good marriage to an IP rocketship. Good motoring, good sailing, and great motorsailing.

Glad you made it back with all your piece parts.


Frankly


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