Hurth Transmission problem

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Dean P

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Jan 22, 2008
9
Oday 30 na
I was out sailing yesterday only for about an hour or so with very light wind (with the transmission in forward gear by mistake) when eventually the wind died so we dropped sails and motored on at low to mid rpm. After about 30-40 minutes the motor all of a sudden seemed to increase in pitch and clattering noises heard which sounded like something let loose. I immediately idled down the engine and went below to inspect. I did not notice anything unusual/loose/damaged and at the lower idle speed everything sounded normal. We turned the boat around to head for home when we noticed we were no longer moving forward. Shifing the gear from forward, to neutral to reverse did nothing. Back below I noticed the prop shaft was not spinning nor was the output to the transmission. I manually shifted in and out of forward and reverse from the lever on the side of the transmission with no result. I can turn the prop shaft with my hand and there's no apparent resistance while doing so. I checked the transmission fluid and the level looks fine.

Now, I always sail with the transmission in neutral but this time forgot to shift out of forward when I shut the engine down before sailing. I know there are a couple different warnings in the manual against doing this as damage to the transmisson will occur. I'm wondering first if you think that doing this caused my transmission problem and second what the problem may be - ie. simple fix or a complete rebuild/replacement. The engine runs fine and I think the clattering/vibrating noises I heard were just the result of the engine being run at a higher rpm without load once the transmission failed.

The transmission is a Hurth HBW-50 2:1 mounted on a Universal M-20 engine.

Looking forward to your responses - Thanks!
 
C

Calif. Ted

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Jun 8, 2004
2,977
Catalina 320 Dana Point
I think almost everyone has

left the transmission in the wrong gear without the kind of result you had. I'm gonna guess your problem lies in the damper plate and flywheel area (perhaps) might want to check with the people at attached website, they have those trannies on sale if all else fails.
 
M

Maine Sail

Sorry but it's..

Time for a rebuild or new. There are lots of known failures of the HBW-50 and there is some good info and discussion over on the Ericson owners association web site.

Unfortunately leaving it in forward is probably what drove the nail in the coffin.. Always neutral or reverse.

Ericson Owners Forums:
http://www.ericsonyachts.org/mainframe.htm
 
higgs

higgs

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Aug 24, 2005
3,715
Nassau 34 Olcott, NY
Hard to believe...

that leaving it in forward one time was the cause of failure. If so, it is certainly not a very robust trans.
 
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Dean P

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Jan 22, 2008
9
Oday 30 na
Good info - thanks

I've been researching all day on this. It appears I have to remove the bell housing to be able to remove the transmission. However, it the problem is the damper plate, it this accessible after removing the bell housing with transmission still attached? Once I remove the bell housing, is there a seal/gasket that will need replacing? There's no fluid behind the housing is there? Thanks.
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
BTDT

Yes, you get to the damper plate by removing the bell housing. There is no fluid in there unless you have a seal failure either from the engine rear seal or tranny front seal. No seals or gaskets needed, again, unless one is failed.
 
H

Hermit Scott

Question

When you guys say damper plate, is that the clutch plate looking thing? Also how does leaving it in gear cause something to fail?
 
Don S/V ILLusion

Don S/V ILLusion

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Sep 25, 2008
7,594
Alden 50 Sarasota, Florida
damper plate

Damper plates are designed to prevent gearbox rattle at low engine speeds, which allows an engine to operate through its entire RPM range. Today's marine diesels are designed with lightweight flywheels which do not create the inertia of an older heavy flywheel. The lighter flywheels result in gear chatter or rattle at low RPM's. This rattle translates into gear wear and damage to the drivetrain.
From the desc above I found elsewhere, it sounds like this may be the source of the noise but not necessarily the failure point this plate is designed to protect
 
D

Dean P

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Jan 22, 2008
9
Oday 30 na
I sure hope it's the damper plate

From what you guys suggest and from what I could find out reading other forums, the damper plate makes sense and best matches the type of failure I have.... I hope! I plan on removing the bell housing and transmission this week sometime to see. IF the transmission is damaged as well, from the info I got so far I think it makes sense to go with new rather than try to rebuild, and while I'm at it step up to the ZF100 as well, as the ZF50 isn't made any longer. I think I will have enough shaft left to get the packing nut/gland out after subtracting an inch. But, hopefully I won't have to go there. I'll let you all know. Thanks for the feedback.
 
C

Calif. Ted

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Jun 8, 2004
2,977
Catalina 320 Dana Point
Rats, That's depressing, I've got one with

873 hrs. on it behind a Perkins, knock on wood.
 
D

Dean P

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Jan 22, 2008
9
Oday 30 na
Looks to be just the damper plate

I opened up the bell housing last night and found the damper plate in pieces. All the springs came tumbing out of the bottom of the housing. The three rivetted studs holding two of the plates together were sheared off. The good news is the transmission seems fine. I could turn the input shaft and the output shaft turns accordingly depending on if the shifter is in forward, neutral, or reverse. Very smooth, no feeling of anything loose or worn. I guess I'll find out when I put it back together and try it under load.

Found the new damper plate online for $84. And I thought fixing this problem would cost well more than my $600 SeaTow bill !
 
Witzend

Witzend

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Dec 25, 2008
1,580
catalina 310 Elk River
Dean,
1) Where did you find the plate for $84?
I'm getting some rattling in neutral at idle and low RPMs with my HBW 50, driven by my M25XP installed in a 2001 C310. The manual indicates worn damper plate.
2) Also, how much room did you need to slide the bell housing back in order to expose and remove the damper plate? I recognize you have the M20, so the space required may be different.
The distance between the prop shaft when disconnected and slid back to the packing nut and the tranny output coupling face would seem to dictate the amount of space allowed to separate the bell housing. I have maybe 3”, is that enough; otherwise I may have to pull the engine, yuck!
3) On the attached view, and I know the drawing is small and is for the M25XPB, but item #8 (a small disk mounted on a collar inside the flywheel) is listed as the damper plate. This does not look like the ones I have seen online for sale with springs in it.
Any information you could supply from your ordeal would be much appreciated...thanks,
Tom
 

Attachments

Witzend

Witzend

.
Dec 25, 2008
1,580
catalina 310 Elk River
Here is the exploded view for the M25XP. Item #13 is the damper plate.
It appears to be different from the M25XPB. Maybe they re-designed this part?
 

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Witzend

Witzend

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Dec 25, 2008
1,580
catalina 310 Elk River
Here is the problem I have with the idea that sailing with the prop in FWD rather in reverse damages this plate. I always sail in REV anyway, but have no idea what the PO did.
The damper plate appears to be designed with stiff springs that would most likely be under a preload.
Although these springs are not designed to run under load in the reverse direction (which is what would happen if the tranny was left in FWD while sailing) I can't believe the force exerted on the springs by the prop sailing at 6 knots would be any greater that the preload force that is already built into the design. My guess is that this plate is a poor design to begin with and that most of the wear is as a result of this poor design.
 
D

Dean P

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Jan 22, 2008
9
Oday 30 na
Witzend, sorry for being a couple months late on this reply (just revisited this thread). In case you or others are stilll wondering where I got that damper plate...

Go2marine.com
162956, Damper Plate Universal, M-18, 1866-050-002
1 @ $83.59 Each

This being said, I can't find this part number any longer at their site. As I remember, there were a couple other sites that had it for around $100 or so.

Torresen has it for much more but the pic in this link is what it looked like.

I was able to uncouple the prop shaft from the transmisson and slide the prop shaft back out of the boat a few inches which was enouph to slide the bell housing out. It doesn't need to slide straight back more than an inch or two (as it slides out of the damper plate). I moved it aside and installed the new damper plate. Replacing the bell housing was a little difficult with one arm leaning into the space behind my engine. Because it has to be perfectly lined up I ended up squeezing myself into the space (I had fun getting out after) behind the engine, squatting over the stuffing box to use both arms to slip it into the new damper plate.
 
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