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Dual Bravos...same clanking noise???

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Dual Bravos...same clanking noise???

Old 06-07-2021, 07:54 AM
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Default Dual Bravos...same clanking noise???

Bravo 1 clanking.

This just started with both drives (at least I never noticed it before). 1988 Formula 311 SR-1 with hollowed out Silent Thunder swim platform and modified big blocks.

There is a rhythmic clanking noise coming from what seems like the tops (top cover) of the drives.

Discover: I was flushing the motors/drives on the boatlift after an uneventful cruise and did not hear anything strange from the cockpit (over the noise of the engines/exhaust). My wife (standing on the dock, next to the boat up in the cradle lift, near the back of the boat and lower than my vantage point) said she hear a strange noise coming from below the swim platform. I did not think much of it because of all the racket from motors and exhaust flappers, etc…

The next day I motored the boat (15-20 minutes under its own power with full functionality and without incident) to the local boat ramp to pull it out for the month (as I will not be at this property for a few weeks). When I was flushing the motors again in the driveway my wife said the noise was still there…so I got out of the boat and listened.

Analysis: I have a rhythmic clunking/clanking (metallic) noise which seems to be emanating from the tops of BOTH drives. I can FEEL it when I put my hand on the drive. I tried to minimize any additional damage/run time while I trouble shot the issue so here is what I know:

1) Both drives are doing the exact same thing. They seem to function fine but there is a distinct noise.

2) I started the starboard motor (on the hose) and shifted the starboard drive into reverse and drive while idling on the flusher hose…no real change in the noise and the shift was smooth and the prop spun as expected…remember, I just motored to the ramp without incident.

3) I found 2 to 2.5 quarts of “frothy pink” drive lube in each drive and flushed that out with new synthetic drive lube.

4) I restarted both engines (one at a time) and the sound did not seem to diminish.

Any ideas of what this could be? I’m thinking it’s a partial break in either a drive shaft yoke or universal…but I don’t understand how that causes water to get into the lower unit lube. Also, I am surprised at how loud/strong the clanking is and that BOTH drives continued to operate. I am also surprised it happened to both drives at (what I assume is) the same time???
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Old 06-07-2021, 08:03 AM
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One of my Bravo drives did this back in the day. It was the shift fork bouncing around a little. It sounded like a marble bouncing around in the top of the drive. I was told it wasn’t a big deal.

Can you get some audio/video of the noise?
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Old 06-07-2021, 08:05 AM
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Old thread on the subject…

abnormal noise coming from bravo one
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Old 06-07-2021, 08:06 AM
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When you drained the drives, was there a lot of water?
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Old 06-07-2021, 08:50 AM
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Originally Posted by TomZ View Post
One of my Bravo drives did this back in the day. It was the shift fork bouncing around a little. It sounded like a marble bouncing around in the top of the drive. I was told it wasn’t a big deal.
Can you get some audio/video of the noise?
Both bouncing around would explain why it is happening to both drives (as opposed to simultaneous failures). My wife also says it is not as repetitive as I thought...so I like your thinking.
It is like a small hammer/knocking (at least at idle) BUT the video sound is drowned out by the exhaust "music".
Thanks Tom!
Any explanation of the frothy lube oil?
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Old 06-07-2021, 08:53 AM
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Originally Posted by TomZ View Post
When you drained the drives, was there a lot of water?
No (unsuspended) water...but the fluid "looked" frothy (but I have no experience with what it is supposed to look like right after operation). That being said, I have a small sample in a jar and little (to no) water separated out after 24 hours...?
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Old 06-07-2021, 10:37 AM
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odd that it’s happening on both drives...

with that said, did you try replacing lube reservoir caps. they are one way valves that hold pressure and minimize froth and bubbles.

was there anything on the magnets when you pulled drain plugs? How old is the oil? Have you serviced or done anything prior to this event?
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Old 06-08-2021, 03:18 PM
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Originally Posted by 1MOSES1 View Post
odd that it’s happening on both drives...

with that said, did you try replacing lube reservoir caps. they are one way valves that hold pressure and minimize froth and bubbles.

was there anything on the magnets when you pulled drain plugs? How old is the oil? Have you serviced or done anything prior to this event?
Drives were serviced by previous owner about 50 hours ago. Nothing on the magnets (top or bottom). Frothing MAY be "normal" as I have no experience with what it is supposed to look like and so far no water/oil separation.

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Old 06-08-2021, 04:34 PM
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What oil was that? (Brand)
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Old 06-08-2021, 06:11 PM
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Originally Posted by speicher lane View Post
What oil was that? (Brand)
Done by previous owner...I understand Redline.

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