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Old 05-05-2016, 04:24   #136
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Re: Hurth / ZF M15A Transmission Failures

ZF's take on this is:
"
3.5 Sailing or moving in tow
Rotation of the propeller while the boat
is sailing, being towed, or anchored in a
river, as well as operation of the engine
with the propeller stopped (for charging
the battery), will have no detrimental ef-
fects on the gearbox.

IMPORTANT
When the boat is sailing (engine
stopped), the gear lever must be in zero
pos-ition. Never put the gear lever in the
pos-ition corresponding to the direction
of travel of the boat.
Locking the propeller shaft by an addit-
ional brake is not required: use the gear
lever position opposite your direction of
travel for this purpose."

However, a "lot of noise" might mean you have a problem.
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Old 05-05-2016, 06:44   #137
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Re: Hurth / ZF M15A Transmission Failures

Yes, putting a zf/hurth gear astern is the acceptable method of stopping the prop.


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Old 06-05-2016, 03:13   #138
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Re: Hurth / ZF M15A Transmission Failures

Thanks Guys
Rgds
Will
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Old 06-05-2016, 04:05   #139
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Re: Hurth / ZF M15A Transmission Failures

Lots of noise in neutral could mean the damper plate is the problem, not the gear box. But you have to remove the gearbox to get to the damper plate.
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Old 25-06-2020, 06:43   #140
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Re: Hurth / ZF M15A Transmission Failures

Quote:
Originally Posted by Jetexas View Post
I just finished rebuilding a Hurth ZF5 transmission for my 2 cylinder Phasor project.

When I bought it, it had reverse but no forward. Upon disassembly I found very little wear on the clutches and the shifter was properly click the output shaft into forward and reverse. However, the gears on the input shaft were not connecting with the output shaft.

There are ring shims that are fitted on the ends of the shafts under the caps to properly align the input and output gears, so that they engage. The exploded diagram shows four shims on each shaft, but when I disassembled mine, I found three shims on the input shaft and two on the output shaft.

When I reassembled it with the same amount of shims, I had reverse, but it totally locked up in forward due to poor gear alignment. By trial and error I found that proper shifting and engagement actually precluded the use of any shims.

I get the feeling that the gears in these Hurst ZF boxes shift slightly on the output shaft over time and the alignment of the gears is actually a bigger cause of failure than clutch plates and bearings.

But then again, who knows what my box actually went through in its previous life, and I'm just a random guy with a workshop manual and a wrench.

Phasor does put weird looking damper plates on their motors.
It's 2020. I have a VP MS10A-B gear that I am rebuilding as an amateur. It is nearly identical to the ZF Hurth M10 as far as I can tell. I took the unit to the local VP repair shop and they said they don't repair them any more but recommended someone locally so i contacted them but they have stopped repairing them too because there were too many problems.

The symptom was that shifting into gear became more sluggish over a period of time. The unit has about 1600 hours on it. The oil was probably never changed but the level was checked frequently and the oil remained clear. I see that when checking the oil that the dip stick should not be threaded in; I wasn't doing that so the oil may have been continuously low.
On inspection, the two thrust washers showed little wear and measured identically. The friction discs had little wear but one of them was cupped.
I got new friction discs and have new taper bearings and needle cages.
(see attachment for output shaft stack).
I measured the output shaft carefully from coupling shoulder to end of shaft.
I measured all the components that would stack onto the shaft so I could double check that no gaps were introduced during assembly. After pressing, the stack measurement proved out with a 0.047" recess from the end of the shaft to the taper bearing inner race. All went well until I torqued the bolt to the specified 44lb-ft.
At that point, the small gear (forward) on the output shaft would not turn because the taper bearing has pressed the thrust washer hard up against the gear. My guess is that because the inner race of the bearing has a bell end, that it is dishing the 0.138" thrust washer as the bolt is torqued.
The situation can be relieved by backing off on the torqued bolt, then tapping the gear up to push the thrush washer toward the end of the shaft, then tapping the gear down to separate the gear from the thrush washer. The transmission shifts correctly on the bench.

Something I can't reconcile: when I first inspected the gear, there appeared to be at least a millimetre of space at both clutch plate sets. Now there is almost none at the troublesome bolt end. The new clutch discs are the same thickness as the old ones, if not 0.0005" thinner.

My dilemma is what to do next? My inclination is to Loktite the bolt at less than the specified torque so the gear can turn freely. Then continue to reassemble with attention to minimizing the taper bearing end play.

Anybody still out there to comment?
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Old 03-10-2020, 14:36   #141
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Re: Hurth / ZF M15A Transmission Failures

Good read about hurth gears as I have trany problems. I remember seeing a sticker next to the atf fill bolt that has gone missing so I can't identify the model. So anybody know how to id ? The case on the port side has in the casting "HURTH made in Italy". and "38062 ARCO ITNI" the I's may be 1's. The existing sticker says ATF only. It's on a OM636 mercedes 43 hp in a 35' sailboat. Thanks for any help....
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Old 03-10-2020, 14:46   #142
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Re: Hurth / ZF M15A Transmission Failures

Continuation....this is about an old boat engine and boat built in 1983 in merry old england. Anyone know of a place in mid Atlantic that stocks rebuilt units off the shelf or stocks parts for when I figure out what I have. Thanks again for reading.
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Old 03-10-2020, 18:11   #143
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Re: Hurth / ZF M15A Transmission Failures

Quote:
Originally Posted by rossny View Post
Good read about hurth gears as I have trany problems. I remember seeing a sticker next to the atf fill bolt that has gone missing so I can't identify the model. So anybody know how to id ? The case on the port side has in the casting "HURTH made in Italy". and "38062 ARCO ITNI" the I's may be 1's. The existing sticker says ATF only. It's on a OM636 mercedes 43 hp in a 35' sailboat. Thanks for any help....

Can you post a picture of the transmission?
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Old 03-10-2020, 21:36   #144
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Re: Hurth / ZF M15A Transmission Failures

Quote:
Originally Posted by Jetexas View Post
To be fair, one of the cruisers in this thread that went through four transmissions later found out the PO had put a left-hand prop on the right-hand drive motor, so he was essentially running them in reverse.
The gearbox reverses the input shaft rotation so a right handed engine should in fact have a left hand propeller.
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Old 04-10-2020, 02:28   #145
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Re: Hurth / ZF M15A Transmission Failures

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Old 22-04-2021, 04:41   #146
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Re: Hurth / ZF M15A Transmission Failures

I've found this thread as I have a ZF M15a with volvo badges on it.
similar symptoms takes a good ten seconds to engage forward drive but ok in reverse.
I've taken it apart based on a lot of quite crude you tube videos.
I have the ZF assembly manual but it doesn't give any inspection advice.
before I disassembled the gear assembly there was a big difference in the gap between the reverse clutch plates and the forward set.
the driven plates show minor visual wear but nothing measurable missing from the thickness. no signs of overheating but they don't appear totally flat.
the friction surfaces all still have the grooves visible I don't know how thick they need to be but appear in nice condition.
the bronze faced thrust washer that is often referred to as a culprit is still bronze faced its not as badly worn as many shown on the youtubers films.

The ZF service manual talks about checking the lever throw and that it must be equal in both directions. I didn't find that bit until Id taken the box apart but the advice given if its unequal 'replace the gearbox'!
I can only guess it was uneven .

I'm concluding that these gearboxes don't break they just need to be properly adjusted. That's the bit I am stuck on.



Anybody still out there to comment?[/QUOTE]
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Old 22-04-2021, 09:20   #147
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Re: Hurth / ZF M15A Transmission Failures

My unit is a Volvo Penta MS10A-B so the following may not be applicable. I am running a LH prop which improperly reverses FWD vs REV but others have said that it's not an issue; my gear runs cool.
What I found was that the thrust washer on the blind end of the output shaft was worn, not on its friction face but on the inner face where it bears against the spacer sleeve. As I torqued the end bolt during reassembly I found that shifting was impossible. The problem was that the bearing inner race was dishing the thrust washer that was hard up against the gear face. I turned a brass spacer approx. 0.030" thick. and a spacer sleeve 1.307" long. The endo slack upon final assembly was approx. 0.017" at each clutch plate stack. See attachments.
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Old 23-04-2021, 05:58   #148
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Re: Hurth / ZF M15A Transmission Failures

Quote:
Originally Posted by bigshineybike View Post
I've found this thread as I have a ZF M15a with volvo badges on it.
similar symptoms takes a good ten seconds to engage forward drive but ok in reverse.
I've taken it apart based on a lot of quite crude you tube videos.
I have the ZF assembly manual but it doesn't give any inspection advice.
before I disassembled the gear assembly there was a big difference in the gap between the reverse clutch plates and the forward set.
the driven plates show minor visual wear but nothing measurable missing from the thickness. no signs of overheating but they don't appear totally flat.
the friction surfaces all still have the grooves visible I don't know how thick they need to be but appear in nice condition.
the bronze faced thrust washer that is often referred to as a culprit is still bronze faced its not as badly worn as many shown on the youtubers films.

The ZF service manual talks about checking the lever throw and that it must be equal in both directions. I didn't find that bit until Id taken the box apart but the advice given if its unequal 'replace the gearbox'!
I can only guess it was uneven .

I'm concluding that these gearboxes don't break they just need to be properly adjusted. That's the bit I am stuck on.



Anybody still out there to comment?
[/QUOTE]
Hi bigshineybike,
It looks like worn clutch plates to me. My Hurth come ZF10 had a similar problem slow to engage in forward but OK in reverse until it would not engage at all in forward. Solution order new clutch plates and install on the work bench. Not cheap it cost me A$600 for the clutch plates from ZF 10 years ago but solved the problem.
Hope it works out well for you.👍🤠
Michael
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Old 23-04-2021, 10:00   #149
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Re: Hurth / ZF M15A Transmission Failures

My gear, a vp MS10A-B had clutch plates that measured 0.0545" to 0.0550". in thickness. The new ones were actually half a thou thinner than the originals.
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