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Old 05-05-2015, 10:29   #16
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Re: Scary, loud, intermittent transmission/bearing noise

hmmm...where the hell is skagit city, wa?? probly has another name! i`m a former laconner high skool person...clyde
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Old 05-05-2015, 10:40   #17
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Re: Scary, loud, intermittent transmission/bearing noise

Do you have this problem in both forward and reverse? I would check and see if the engine mounts are OK. This sounds like a problem I had when reversing, the frame of the engine would vibrate against one of the engine mounts due to bad alignment. Made the whole boat vibrate with a horrible sound...
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Old 05-05-2015, 11:08   #18
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Re: Scary, loud, intermittent transmission/bearing noise

Another thing to check is the shaft coupling, both flanges. Remove bolts to see if the holes were previously worn with just the bolts replaced. The shaft coupling can be cast iron w/cracks thru bolt holes.
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Old 05-05-2015, 11:29   #19
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Re: Scary, loud, intermittent transmission/bearing noise

The sound you describe is how I would describe the noise generated when...

My boat had been on the hard for a couple of years, with the engine started intermittently to keep it lubed to avoid rust.

I decided that the tranny needed to be rotated to lubricate the bearings and gears, so I engaged the transmission to rotate it a bit to splash the oil in it around.

The dry cutlass bearing began to howl with a mid-frequency moan that vibrated the whole boat.

I didn't do that again.

My guess is that it is coming from the stern tube/cutlass bearing.
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Old 05-05-2015, 12:08   #20
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Re: Scary, loud, intermittent transmission/bearing noise

We certainly seem to have a consensus building that I'm going to need to look closely at the cutlass. It's only a few years old, but if we had an alignment problem, then that would make sense. The sound seems to be worse standing at the helm than it does staring at the transmission. Maybe that's because it's coming up through the hull where the cutlass is attached to the sting.

Am I going to need to pull the prop shaft to inspect it properly? That means pulling off the prop and the coupling (so I can slide it past the rudder) which is not an easy thing to do.

I'll need to check engine alignment before we pull out, I guess. The coupling is new, but the transmission is old, so I'll inspect the bolt holes on the transmission side.

The prop will also need to be inspected. I've looked at it underwater with a snorkel not that long ago and it seemed fine, but worth playing with on dry land.

Thank you so much for all your help. You guys are amazing.
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Old 05-05-2015, 12:33   #21
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Re: Scary, loud, intermittent transmission/bearing noise

I have a Hurth v drive on my Westerbeke. The dip stick came loose from the cap and fell down into the case. Luckily it did'nt go through the gears...only got chewed up a bit. Anyway, its a quick check to see if that's the problem. Good luck.
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Old 05-05-2015, 12:50   #22
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Re: Scary, loud, intermittent transmission/bearing noise

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I have a Hurth v drive on my Westerbeke. The dip stick came loose from the cap and fell down into the case. Luckily it did'nt go through the gears...only got chewed up a bit. Anyway, its a quick check to see if that's the problem. Good luck.
Thanks, SD. I checked the oil in the Hurth last night and the dipstick was there. Good thought, though. It would have maybe explained the intermittent nature of the issue if there was something loose floating around in there.
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Old 05-05-2015, 13:02   #23
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Re: Scary, loud, intermittent transmission/bearing noise

If it's the Cutlass, you should be able to feel play in it if you dive on it.
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Old 05-05-2015, 13:05   #24
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Re: Scary, loud, intermittent transmission/bearing noise

Not sure if you were aware of this info or not. When you say Sting do you mean Stave bearing?

Replacing A Cutlass Bearing (Sleeve Bearing) Photo Gallery by Compass Marine How To at pbase.com

Also when you have the shaft out make sure there is no movement where the strut joins the hull.
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Old 05-05-2015, 14:03   #25
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Re: Scary, loud, intermittent transmission/bearing noise

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Not sure if you were aware of this info or not. When you say Sting do you mean Stave bearing?

Replacing A Cutlass Bearing (Sleeve Bearing) Photo Gallery by Compass Marine How To at pbase.com

Also when you have the shaft out make sure there is no movement where the strut joins the hull.
Sweet. Thanks, DeepFrz. Good old MaineSail. I should have known he'd have something.

When I say sting I mean strut. Just couldn't find the right word in my brain!
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Old 05-05-2015, 14:13   #26
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Re: Scary, loud, intermittent transmission/bearing noise

Is there any possibility that some part of the engine or transmission is touching the boat? That could include hoses, cables, and wiring.

I used to get a horrible rattling noise at a certain RPM which reverberated through the cockpit. I found the cause by accident one day : the vented loop in the raw water hose was touching the cockpit sole. This was enough to telegraph lots of noise to the cockpit sole.
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Old 05-05-2015, 16:20   #27
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Re: Scary, loud, intermittent transmission/bearing noise

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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.
Long screwdriver to your ear or stethoscope to isolate the noise is a good first step.

I'm with deepfrz. Alignment issue? A tiny misalignment can load the trans such that you may be sideloading the internals. It doesn't take much to get contact through a band, clutchpack or planetary gearset.

Do you get the noise in reverse? Do you have play in your trans output shaft? Loose or misaligned engine mounts? Engine to trans loose? Anything grounded in contact with the engine or trans? Exhaust preload?

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Old 05-05-2015, 17:07   #28
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Re: Scary, loud, intermittent transmission/bearing noise

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Long screwdriver to your ear or stethoscope to isolate the noise is a good first step.

I'm with deepfrz. Alignment issue? A tiny misalignment can load the trans such that you may be sideloading the internals. It doesn't take much to get contact through a band, clutchpack or planetary gearset.

Do you get the noise in reverse? Do you have play in your trans output shaft? Loose or misaligned engine mounts? Engine to trans loose? Anything grounded in contact with the engine or trans? Exhaust preload?

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Good questions, though it seems that such a misalignment would be a constant problem and not turn on suddenly?

I've never had the noise in reverse, but that doesn't mean it wouldn't happen if I spent hours in reverse.

It's a v-drive, so there's no output shaft. The engine is new and there doesn't seem to be play in the mounts. Nothing is loose, and nothing is in contact.

I definitely need to re-check the alignment. We had a mystery rattle (totally different from this current moan) as I pulled away from the dock after the engine swap. As part of the troubleshooting, the mechanic re-checked the alignment and declared it good. I wasn't watching while he did that, though, as I was in the water in my underwear tightening up the shaft zincs (which were the true source of the noise).

PNW water is delightful in March!
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Old 05-05-2015, 18:01   #29
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Re: Scary, loud, intermittent transmission/bearing noise

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PNW water is delightful in March!
Yup. And associated shrinkage creates its own "harmonics"...
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Old 05-05-2015, 18:14   #30
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Re: Scary, loud, intermittent transmission/bearing noise

LOL - talking about shrinkage try the water off the dock in Wells Gray Provincial Park.
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