Crunch crunch in gear....

M

MarkA

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Coming back from Catalina yesterday, something started crunching down below. My stomach tells me there's a hunk of loose metal in the transmission, but I haven't seen evidence of that--yet. Could it be the cutlass bearing?

Perkins Perama M30 motor, Hurth 50 transmission. Motor runs great in neutral. Put it in gear, and intermittent crunching and popping sound at low RPM from somewhere in the vicinity of the prop shaft. At high RPM, no crunching sound. Transmission fluid is crystal clear on the dip stick, but I haven't drained it yet. In neutral, I can turn the shaft by hand, and it feels smooth with no grinding or sticking points. Eventually, we took the risk and ran it for 3.5 hours at cruising speed, and there were no problems or odd sounds.

Any ideas?
 
bayhoss

bayhoss

Member III
Can you get under the boat to have a look at the prop, shaft, and maybe give a wiggle to check the cutlass bearing?

Best,
Frank
 
M

MarkA

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bayhoss said:
Can you get under the boat to have a look at the prop, shaft, and maybe give a wiggle to check the cutlass bearing?

Best,
Frank
Click to expand...

Gross. That means diving in the Main Channel of LA Harbor. I'll give it a try.

What wiggle am I looking for? Lateral movement of the shaft at the bearing?
 
G

Glyn Judson

Moderator
Moderator
Haul that sucker.

Mark, Haul the boat to survey it properly on land. Chances are that if it is associated with the shaft, strut, cutlass bearing or prop, you'll need to get it on land anyway for the repair. So what happens if you do dive the boat, can't get enough leverage to make the shaft, etc. to move and rattle and you go back to running the boat under power and something more drastic or more expensive results? If it were my boat, I'd haul that sucker and right now. This coming from a guy who just hauled over the weekend to paint the bottom and went back in the drink at 1000 yesterday. While I was at it I checked all that moving stuff too and it was OK. Glyn Judson
 
bayhoss

bayhoss

Member III
Hauling is always best, As it tells the whole story. You should have no play in the cutlass bearing and wiggling the prop will make certain of that. What I was more referring to by diving under the boat is the presence of debris that may be wrapped or tangled in the prop, shaft, or strut.

Hope this helps,
Frank
 
M

MarkA

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Loren Beach said:
http://www.ericsonyachts.org/infoexchange/showthread.php?7444-Prop-Comparisons&referrerid=28
See reply 6 and 7.
Hope you do not find any problem remotely like this one!
No alligators in Catalina, right?
:rolleyes:

Good luck on finding a solution!

Loren
Click to expand...

Loren, that boat was ancient (three hulls before mine), so I shouldn't have that problem yet ;)

My prop seems fine. I peered at it from a dinghy with a spotlight, and it looks good. Also, there was no vibration or loss of speed at cruising speed.
 
M

MarkA

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rwthomas1 said:
I'm guessing that the damper plate has failed. Its a guess and I hope I'm wrong.... RT
Click to expand...

Hmmm, that should be easy to replace, right? I'll drain the transmission today and see what shiny bits come out. If nothing, I'll move on to the damper plate. I don't want to haul out yet, as I'm still stockpiling cash for a much-needed paint job and don't want to haul out twice.

-mark
 
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
rwthomas1 said:
I'm guessing that the damper plate has failed. Its a guess and I hope I'm wrong.... RT
Click to expand...

And, if it's a broken damper plate spring, a piece of broken spring can turn sideways and stop the engine in one rpm.... a friend of mine actually had this occur in his vintage Pisces/Isuzu.

LB
 
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G

Glyn Judson

Moderator
Moderator
Whaaat?

All, This is a new one on me. OK, I give, what's a damper plate? Do I have one in my Kanzaki (read Yanmar) transmission or is it something unique to Hurth? Glyn
 
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Glyn Judson said:
All, This is a new one on me. OK, I give, what's a damper plate? Do I have one in my Kanzaki (read Yanmar) transmission or is it something unique to Hurth? Glyn
Click to expand...

I'm betting that you have one. It is a listed replacement part for a Yanmar engine, per an on-line source.
It's a steel (?) multipart plate between engine and the transmission. On our engine there are springs arranged around the outside. The springs are supposed to "dampen" out the sharp power pulses somewhat from the engine and ease the shock load on the transmission, or so I'm told.
To me, the spring part resembles the clutch pressure plates I once installed in an old car.

Loren
 
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M

MarkA

Please Contact Admin.
Wait a minute....

The damper plate rotates while the transmission is in neutral, correct?

If so, wouldn't we expect it to exhibit symptoms of failure while the motor is idling? There are none. It only crunches in gear, and, so far, only at low rpm.

Ok, I'm headed to the boat now--and feeling a little nauseous.

-mark
 
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
MarkA said:
I know nothing about Dr. Diesel. What should I learn???
Click to expand...

Check out a veritable avalanche of critical posts, from near and far, new and older, on other big forums like those at SBO or SailNet. This being the internet, it's easy to dismiss one or two whiners, but that particular business is one of the most widely-excoriated on the boating 'net.
:0
Many of the critical narratives are painfully detailed....

LB

ps: is the drive train in a 34T a V-drive? If so, might that make the work easier... or harder?
 
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M

MarkA

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Mystery Solved, I think. Dammit.

Drained the fluid. Although it was mostly a clear cherry syrup color, there were tiny goldish/silverish sparkles on the surface--just pinpoints of light. I panned the bottom of the white drain pan as though I were searching for gold, and found some dull, grayish, flakes about the size of the glitter a kindergartener uses to make Mother's Day cards. It felt gritty in my finger tips.

While rotating the shaft with both the dipstick plug and bottom drain plug removed, I heard a slight clicking sound in certain positions--particularly when I rotated the shaft back and forth. How much play is normally present between the gear mesh?

If I lost a gear tooth, I would have expected to see more grit than I found. On the other hand, I don't like what I found. Is it normal to find some grit?

Where is the best place to have a Hurth HBW 50 rebuilt?

-mark
 
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