Scary, loud, intermittent transmission/bearing noise

[cwyckham]

Help!

I've been dealing with a mystery sound ever since I re-engined with a Beta 35. The install was professionally done by an mechanic with an excellent reputation. Only the engine was changed, the transmission, coupler, shaft, etc. all stayed (boat stayed in the water).

My mechanic isn't local and he's convinced it couldn't be anything he did.

System:

• New Beta 35
• Existing Hurth V-drive (original approx 2500 hours on it)
• coupler with key
• PSS dripless seal
• cutlass bearing
• autostream feathering propeller

Symptoms:
Loud moan starts randomly. It isn't a harmonic type thing that's always there at a particular rpm. It will suddenly start like somebody flicked a switch.

It is very loud and shakes the soles of your feet as you stand at the wheel. Hard to type out what the frequency is. Sounds like an adult male saying Ahhhhh... to the dentist but a lot louder. Not a squeal.

Resolves immediately if you drop rpms to idle for a few seconds or pop into neutral. Will then be fine for a while (minutes to hours) and then come back suddenly.

My mechanic had thought that this might actually be the PSS seal. If it's too loose it can chatter and make a loud noise. I adjusted it per manual (it seemed fine when I checked).

The sound stopped for a while after that, and I thought that might have been the issue. However, it's back (and getting more frequent), and I've just checked the seal and it hasn't moved since my adjustment.

The transmission fluid level is fine and still looks red.

Sorry this is getting so long, but I wanted to get it all out there.

On Saturday, we motored for a couple hours. There is a lot of growth on the boat, so there probably is on the prop as well. There was more vibration than usual when motoring and this may have contributed to the fact that the "moan" started up again.

As the day went on, it became worse and worse. By the time we were approaching our slip, it was happening every few minutes (though still resolving with a drop of the throttle for a few seconds).

Any ideas what this could be? My thoughts:

• Transmission: Spun bearing?
• PSS: could be, but sure seems loud for that.
• Cutlass bearing: Bearing is only a few hundred hours old, but maybe spinning in the mount intermittently?
• Something to do with the prop? Seems that this would be more of a shake than a moan as it wouldn't be transmitting directly into the hull

Thanks in advance for your help. We're hauling out in the next few weeks and I'd like to have some ideas of what to check while we're out of the water. Other than the haul-out, we're stuck in the slip until I can get this fixed.

[shakey doug]

try opening the seal and applying a little petroleum jelly on the shaft where the o rings run being careful not to get it on the seal faces.

[Sailmonkey]

Originally Posted by shakey doug

try opening the seal and applying a little petroleum jelly on the shaft where the o rings run being careful not to get it on the seal faces.

Those orings never move.....I fail to see how lubricating a stationary object will make it stop making sound.


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[a64pilot]

I'd guess Cutlass bearing, but not rotating in it's housing, the shaft vibrating.
Often noises like this are accompanied by a vibration, sometimes you can track down what is vibrating when the noise is present.
Be careful around rotating components though, don't have loose clothing, long hair near them.

[DeepFrz]

A mechanic's stethoscope may help you to narrow down the area of the sound. It may be very difficult to pin point the source of a sound. The engine/transmission/v-drive could be setting up a sympathetic vibration in a bulkhead or even in the hull in the least likely of places. Or it could be coming directly from the engine/transmission/v-drive. Probably impossible to diagnose remotely and you will need assistance in isolating the sound.

However, check your engine alignment. Check the shaft for wobble. Is the cutlass bearing mounted in the hull or in an external mount? If external, check the area around where the mount is attached to the hull. Walk around the boat and see if you can isolate any loose structural item that may cause this type of sound. What was removed/replaced when the engine was installed? The fact that it responds immediately to a change in RPM and might not come back for hrs. makes me think its a sympathetic vibration in the boat structure. Good luck.

[deblen]

Remove air intake filter & see if noise stops.Thinking a vibrating filter or something in air intake vibrating.Had it happen once.
Does it happen if you shift to neutral when noise starts?

[DeepFrz]

Len, yes, good place to start.

[cwyckham]

Originally Posted by DeepFrz

A mechanic's stethoscope may help you to narrow down the area of the sound. It may be very difficult to pin point the source of a sound. The engine/transmission/v-drive could be setting up a sympathetic vibration in a bulkhead or even in the hull in the least likely of places. Or it could be coming directly from the engine/transmission/v-drive. Probably impossible to diagnose remotely and you will need assistance in isolating the sound.

However, check your engine alignment. Check the shaft for wobble. Is the cutlass bearing mounted in the hull or in an external mount? If external, check the area around where the mount is attached to the hull. Walk around the boat and see if you can isolate any loose structural item that may cause this type of sound. What was removed/replaced when the engine was installed? The fact that it responds immediately to a change in RPM and might not come back for hrs. makes me think its a sympathetic vibration in the boat structure. Good luck.

This is interesting. I'd basically ruled out a sympathetic vibration because it comes on so quickly (like flicking a switch) and seems pretty insensitive to rpm. It needs a very large drop in rpm to go away.

Good idea to check engine alignment. It's on the list. I can't quite figure out how that would cause these odd symptoms, but it's worth a check.

The sound is so loud that when I'm in the engine compartment, it seems to come from everywhere at once. I do need to try to spend more time in there when it's happening. I worry that it's doing damage, though, so my first instinct is always to make it go away, not play with it. I guess I need to fight that instinct.

It is an external "sting" mount for the cutlass bearing.

[cwyckham]

Originally Posted by deblen

Remove air intake filter & see if noise stops.Thinking a vibrating filter or something in air intake vibrating.Had it happen once.
Does it happen if you shift to neutral when noise starts?

It immediately goes away when I shift into neutral. I'm pretty confident it isn't in the filter. It shakes my feet.

I wish it was easier to describe these sorts of things in text!

[Uncle G]

I agree with a64pilot. Sounds like the shaft could be vibrating in the cutless bearing - especially since it immediately stops if you go into neutral.

Maybe your previous engine was badly aligned and wore the bearing on one side - but the shaft was always held firm there by the mis-alignment. Now your new guy has lined the engine up properly, the shaft can start itself vibrating. The hull above the bearing would then amplify the noise.

[northiceman]

I have been getting a little vibration the last 2 years and when I removed the shaft this year I believe I found the problem. The cutlass brg had very tiny hairlike cracks in the rubber (inside the bronze tube). I actually only noticed it when I took a pic with my 16 Megapixel camera-that night I zoomed in and the picture showed how bad that cutlass was. It looked fine to the naked eye and no looseness at all when the prop shaft was in-it was perfectly snug. The cutlass has been there for 19 years and started showing a bit of vibration (only once a day sometimes) after I spent last year in the warm Bahamian waters. The rubber is very dry and was probably about to go.

My guess is the sound you get is definitely in the drive train (that is between the engine/tranny drive coupling and the cutlass). One other possibility is that one blade of the prop may have been slightly bent ? It only takes about a quarter of an inch! and a bit of current in the water.
You may want to unbolt the prop shaft from the transmission coupling and run the engine with tranny in gear to see if you do get any sound out of the transmission.
Good luck - let us know what it was !

Ron

[GRIT]

I've had a similar event after re-powering as well. In my case it was the cutlass bearing. We re-powered the boat and did a very fine job lining everything up, then the noise started, just as you describe. The old setup didn't make any such noise.

It turns out that the old setup wasn't lined up as true as the new setup. It didn't make noise because the shaft was essentially "wedged" in the cutlass bearing. Being off centre meant that it was reasonably well supported, with little play.

With the new system all properly aligned, the shaft had a slight bit more play, and was less well supported, due to the worn bearing (bottom forward, top aft). I assume it was due to sag in the old engine mounts.

In any case, a new cutlass bearing fixed us right up. No more intermittent moaning from the peanut gallery.

Cheers, and good luck.
Paul.

PS, looks like while I was writing, I ended up late to the party. Consensus seems to be that the cutlass bearing needs to be replaced.

[Wulf]

Long shot & I'm probably way off base but could it be that 1 or more blades on the prop cleared while other(s) didn't? Symptoms don't seem like it but...? You didn't mention how long it's been since the last time you had the boat away from the dock before engine change which got me thinking on this path.

[Cheechako]

Originally Posted by cwyckham

It immediately goes away when I shift into neutral. I'm pretty confident it isn't in the filter. It shakes my feet.

I wish it was easier to describe these sorts of things in text!

Does your shaft still turn when you go to neutral? or does the prop stop it immediately?
For that much vibration I'm thinking cutlass bearing, or maybe the prop you have is causing it... out of balance? causing the cutlass to moan?
Is that an auto feathering prop? If it turns out to be the cutlass already, then you may have a prop or alignment problem.
I would check:
Cutlass
Prop
Alignment/shaft

[bailsout]

I had a wobble in my prop shaft. I never felt or heard anything but only noticed it because while under sail one day I was curious to see how fast the shaft was spinning when I'm neutral. Maybe sailing in neutral will help locate the sound. Maybe it won't growl in neutral while spinning under sail alone. Might help your troubleshooting.