Grinding Noise from Prop Shaft

[jim_thomsen]

We are in Palau, in a nice anchorage but without any haul out lifts for 500 miles and so far no local mechanics to help.

2 days ago, when we were going to explore the area and I put it in gear there was a terrible grinding noise. Until that it has been working fine. We had to motor about 100 hours from Papua New Guinea to Palau last month and then 3 weeks ago had to motor to a safe hole when typhoon Haiyan went over. No issues until this time.

The grinding happens in both forward and reverse. I have checked the prop and everything looks OK. When we turn the prop or the shaft the noise is easy to hear in the engine room but hard to know where it's coming from.
We have a Yanmar 4JH4E engine with a Centaflex flexible coupling and a GORI prop. My plan (unless someone has a better idea!) is to disconnect the shaft/flexible coupling and then be able to isolate the noise to the rear bearing or to the flexible coupling or to the gear box.

I have never worked on a flexible fitting and do not have a manual. There seems to be a number of points I could disconnect it, but which would be best? I want to be able to reassemble it and not have any alignment issues.
To explain better I posted a few photos of the coupling at: Tenaya Travels

Thanks for any help!

Jim

[DRS]

Does it make the same noise if you can manually spin the prop with the gear box in neutral? Have you checked the gear lube in the transmission?

[jim_thomsen]

Yes, DRS, it makes the same sound with the gearbox in neutral and manually turning the prop.

Yes, gear lube level is fine.

[Sailmonkey]

I've never seen one of those, but I would imagine if you mark both halves of the coupling with reference marks, then remove the four radial bolts you'll be able to turn the shaft independently of the trans.
As another thought have you tried removing the shaft brush?

[Sailmonkey]

After further googling, pulling the aft edge radial bolts won't allow the shaft to spin free others trans, but if you mark the flange on the trans In Relation to its mating position on the coupling then remove the four bolts with their heads facing fwd you can then swipe rate the shaft from the trans. When done, realign your marks and bolt back together, the alignment will be intact.

[jim_thomsen]

Thanks Sailmonkey,

I think you are probably right....just wanted to make sure before I tried anything...especially something that's not easy to do.

I haven't removed the shaft brush, but it is tied away from the shaft (maybe that shows in the photo?)

[Bestathook]

You didn't mention examining your cutlass bearing, Did you probe inside the housing and bearing for some kind of hard substance or loss of material?

Also, in the thru the hull tunnel that goes into your shaft seal, is there any thing that got in there, or the rubber boot is there is one?

I don't mean to state the obvious, but you didn't mention checking out those areas.

[Nicholson58]

I think if you disconnect the drive line you should be able to isolate the noise source. As noted above, match mark and photograph everything so you can duplicate the re-assembly.

It looks clean around the coupling so I don't see broken or worn flex elements. It is possible that some of the rubber-metal elements are broken. In you photo, the black rubber ring is vulcanized over tranmission coupling elements. Remove and inspect all these parts for breakage including internal to the rubber ring.

Look around the engine and make sure the engine mounts anre intact and that they have not moved; bolts tight.

If you seperate the shaft from the transmission, you should be able in neutral to rotate the transmission output by hand.

Just a silly question, anything stuck on your prop, shaft etc. under the boat? Barnicles, failed cutlas, failed thrust bearng, sheared keys. Has the prop &/or shaft shifted fore or aft? Folding prop screwed up? Shaft shark misaligned? Your clue that there is the same noise in neutral and hand turning sugests that you might find the source aft of the transmission. Rull out all simple stuff first.

If the noise is ahead of the coupling you are left with the transmission. Obvious questions is oil. Then - is the shifter making full stroke or are you stuck between? We lost part of one end of the red shifter cable inside of the binacle. The short fix without spares was to end-for-end the cable and jury rig the engine end.

Is the niose related to RPM?

I am not familiar with your engine-trani. You might have to pull the tranmission. That would tell you for sure where the noise is. Do you have a mechanic's stethascope? It is remarkably good at isolating noise source. McMaster-Carr about 14 bucks.



If you determine the transmission is guilty you will be into a learnig experience, especially without books. Perhaps you can download a manual.

[jim_thomsen]

Thanks Bestathook,
Please state the obvious...that's probably what I'm missing.
And I have not probed inside the housing. I guess I have been afraid of taking off the rubber boot...thinking maybe a lot of water may come in. Maybe I'm over worried? Since the bottom is 80 feet below I am trying not to have a lot of water come in. I was hoping that freeing the shaft I could move it backwards and see if anything comes out in the water.

If I take off the rubber boot will much water come in? I have only done that when I've been out of the water.

[jim_thomsen]

Nicholson58, Thanks.
We have looked at the prop and it seems fine. But I had not considered any movement forward or backward. We did have a bad time a couple of months ago in Papua New Guinea when our prop snagged a large rope, breaking the rope cutter. But since then we motored probably 100 hours getting across the equator to Palau.
I'll go down again and make an even more detailed check of the prop and shaft.
Thanks for the other ideas.....more to keep me busy.

[Jim Cate]

When a sudden noise erupts with no obvious precipitating event, it is possible that your damper plate may have failed (partially) and that the noise comes from bits hitting the bell housing or other nearby stationary parts. If this is the case, the noise will not change when you disconnect the shaft. Of course, it could be some internal part of the tranny, but sudden failure without some noticeable event is not so common. Damper plates seem to just suddenly fail at times.

Sure hope that it is something simple to fix, mate... good luck!

Oh... what sort of tranny is it?

Jim

[jim_thomsen]

Hi Jim,
We have a Yanmar 4JH4E engine with a KM4AI gearbox.

[delmarrey]

I didn't read all the post so excuse me if someone has already mentioned this.

Some Yanmars use a Kanzaki trans. Those have cone clutches, which are known to have problems at times. They could be not totally disengaging and causing the gears to grind. And other types of trany's will do the same if the plates are gummy.

[Jim Cate]

Jim, I'm not familiar with that tranny, so no specific help from me! But one other thing to check is draining some of the lube fluid, and see if there is a lot of bronze powder or chunks in it. that, of course, is not what you want to see! If the cone clutches that Del mentioned are buggered, some detritus is likely to be present.

Cheers,

Jim

[highseas]

Jim Thomson, if you snagged a rope tight enough to break the linecutter,then you quite possibly also did internal transmission damage.Sometimes it takes a few more operating hrs. before grinding noises start.