reversing gear noise?
 

We started hearing much louder and lower pitch noise while crossing Lake Michigan to Sheboygan WI, and then from there all the way home to Waukegan IL. About 130 miles. We also feel a lot of vibration. I took some videos so you can hear the noise. I'm wondering if it could be the reversing gear causing all the racket and vibration. It doesn't do it if it's in neutral. The propeller is fine and spins without anything odd.

There are two videos exploring the engine area, and one looking and listening in the lazzarette. It's a Columbia 8.7

[YOUTUBE]HN0ZkY-8bpI[/YOUTUBE]
[YOUTUBE]6HNoDPue4RA[/YOUTUBE]
[YOUTUBE]wkgyLLSRY0A[/YOUTUBE]

The noise is most obvious in the last one.

Thanks,
Jim

What happens with the noise when you shift into reverse?
Does the noise vary with RPMs in any way?
The vibration + the noise could be something going on with the prop. The first thing I'd do is get a diver under the boat to rule prop problems in or out.

TRUE GRIT

I inspected the prop from our floating dock with bright sunlight and clear water. I don't see any issue with the prop. I pushed and pulled on it with a boat hook and didn't feel any slop.

I didn't try it in reverse - thought about that on my way home later. What I think I'm hearing is more like the clatter noise reverse always makes. I guess I'll take the cover off and see what I can see.

I can't imagine the prop shaft would be doing it with the bit of vibration it has.

It gets worse with higher rpm. The engine videos were shot at a bit less than normal cruising rpm. The lazerette video was somewhat slower I think.

I changed oil to Mobile 1 4T motorcycle oil before the trip (300 or so miles all together), but of course only about half of the oil gets changed out so it's a blend of dino and synthetic at this point.

Jim,
I'd suggest getting a mechanic's stethoscope and probe around a bit with that. My suspicion is the main bearing at the output of the transmission.

Hi Al,
I think you're right. I went to the boat yesterday intending to pull the prop shaft out of the coupling so I isolate the noise to the engine. But it didn't slip out easily. So instead I opened up the reversing gear and rotated the shaft by hand, in neutral of course. I had my wife take a couple videos for the sound. It's a little difficult to tell, but between what I could hear and feel, I think the output bearing is bad. I don't know how much of the noise is due to other rotating parts in there. I'll have to read up on replacing it. It's probably just a bearing and a seal? Offhand it looks like I can do this with the motor in the boat, but hoping I don't have to take the whole reversing gear out. Wishful thinking?

Here are the videos. Let me know what you think.

[YOUTUBE]2zT9Hb4RFmU[/YOUTUBE]

[YOUTUBE]tKH9tbk5o2Q[/YOUTUBE]

Jim

Reversing gear noise?
 

Jim, if you're referring to what appears to be a clicking sound as you rotate the output coupling back and forth, that is a very normal noise. The stops on each side of the brake band click against the top ledge of the oil pan. If the big ball thrust bearing has failed, you can usually feel some play in the bearing as you tug hard up, down, and sideways on the output coupling. Don

Thank you Don.

No, I'm not referring to the clicking noise, but a lower pitch grumble. It's hard to hear on the videos, but more likely where I'm turning it back and forth, about 38 seconds into the longer of the two videos. I think I felt a less than perfectly smooth bearing but when I pushed and pulled sideways on the flange I didn't feel slop. I think it's easier to hear the "non-normal" sounds in the lazarrette video. It makes a deep rumbling sound in the cockpit and off the hull when I listen to it from the dock. And we feel vibration.

If I end up confirming it's the bearing, I suppose I should change out the toothed adjuster while it's apart. I have access to a press. I have pretty good access to it in my boat. I suppose I should try again to separate the prop shaft to isolate it. It didn't make much noise while running in neutral though.

Jim

Transmission noise
 

Jim, I do hear a noise in the lazarette(sp) video but it doesn't sound to me like the clear noise of a failing thrust bearing. I do admit however that I've never been very good at identifying noises on videos.

I do encourage you to separate the prop shaft from the output coupling before getting involved in any heavy maintenance. If the thrust bearing is failed far enough to be the cause of your noise and vibration, I think that you would surely hear and feel something in the back of the transmission when running in forward at the same RPM. Don

How much fore and aft motion should there be at the output flange? I measure 1/16". I also listened with a mechanics stethoscope and didn't hear anything. The engine cradle was particularly quiet, which tells me it isn't the A4 causing the vibration we feel. I don't this stethoscope has much low frequency response though.
I'm working on pulling the shaft now. I think I'll have to take the coupling off to separate it from the motor.

Ok, so the prop shaft is not sliding out of the coupler if that's what it's called, and I can't separate it from the output flange as an assembly. I don't recall this being a problem when I aligned the engine to the shaft years ago. Am I missing something?

Hmmm. Let's take them backwards.

You should be able to remove the bolts from the back of the coupler and slide the shaft/coupler assy backwards, at least till the prop hits the rudder. Are they stuck? Slip a putty knife between them and open it up for a screwdriver, etc.... There is a pilot bore between the output flange and the coupler that's a pretty good fit, so it may not move without a little help.

I've only done this once, but mine would not slide. It has a key, and a great fit (close to locational interference). I had to use a gear puller, and you only have enough room to do that if the shaft is slid way back, or the engine is out, or both.

Prop shaft and output couplings
 

Jim, the faces of the prop shaft and output couplings have a shallow alignment ridge and recess to keep them aligned with each other which is the only thing holding them together. You may have to temporarily sharpen the tip of a common screwdriver to pry them apart. Don

PBlaster!
 

Great advice! I ground a screwdriver as you suggested and also sprayed the flange with PBlaster and tapped it a dozen or so times. Waited a minute or so then I used the sharpened screwdriver and tapped it gently two times with a 2 pound hammer. It popped off very easily.

So after all that, I ran the A4 through its RPM range and didn't notice any vibrations. So at this point I think it's all the prop shaft, but possibly the prop. We'll be pulling the boat out in a few weeks and I'll pull the shaft at that time.

Thanks again to all,

Jim

Found the cause?
 

So after we pulled the boat for the winter, I thought to look around and found the zinc was very loose on the prop shaft. I'm hoping this would explain the problem I described above. What do you think?

[YOUTUBE]https://www.youtube.com/watch?v=rJJR9y53u-g[/YOUTUBE]

It seems like a small mass to create as much noise and vibration as we experienced, but spinning as fast as it does, maybe so. I'm guessing it wouldn't necessarily cause vibration at the same speed as the prop since it's loose so maybe that explains the lower frequency of the noise/vibration relative to normal engine sounds.

Jim

A tiny imbalance at 2,000 RPM can do a lot ;)

I guess I never closed the loop on this one. For 2017 season I simply left the zinc off the shaft. We had a late start due to health issues but it ran smooth and quiet when we finally got out on the lake.

Thanks for help guys,
Jim

Thanks Jim.
Note to self: rumbly sound in A4 could be lose zinc.