Who has a ZF BW7 transmission?

[prroots]

Our new-to-us Beneteau 411 came with a Westerbeke 44A FOUR engine and ZF BW7 transmission. We would like to know what gear others leave the transmission in while sailing. There seems to be a conflict between what the manual says and virtually all dealers and transmission shops
Pete

 

[Stu Jackson]

And just what are those differences? It sounds like a Hurth transmission. I'd go by their website/manual information, rather than word of mouth.

Here's an example: http://www.c34.org/wiki/index.php?title=The_Right_Transmission_Gear_for_Sailing

 

[prroots]

And just what are those differences? It sounds like a Hurth transmission. I'd go by their website/manual information, rather than word of mouth.

Here's an example: http://www.c34.org/wiki/index.php?title=The_Right_Transmission_Gear_for_Sailing

We've concluded our communications with Westerbeke since (apparently) nothing further is to be learned. They insist the gear should be left in Forward or Neutral. They also recommend we consult our local Westerbeke dealer who has confirmed it should be left in Reverse. The master distributor says it can be left in Forward or Reverse without damage whereas Westerbeke says the clutch will be damaged if left in Reverse. I don't recall every receiving so much contradictory information from so-called official sources. Do you wonder why we're confused
Pete

 

[Maine Sail]

Proots,

Your BW-7, I believe, is a cone clutch gear box that is similar in design to a Kanzaki/Yanmar box and not similar to a typical Hurth/ZF box that uses clutch plates. I think the only engines they were used on were some Bukh's and a few Westerbeke models. The BW-6 I know is a cone.

They were built by a Spanish subsidiary of ZF called INDUSTRIAS SUBSIDIARIAS AVIACION SA but are not Hurth's..

With most cone clutches neutral is preferred and the manual states this. I, like you, would strongly question that "forward" will not damage this box.

Yanmar/Kanzaki go so far as to specifically prohibit locking it in any gear while sailing and suggest a shaft brake if locking is desired. Their boxes are also cone clutches. I suspect Westerbeke knows little about what will harm this box having sold so few of them compared to the Hurth/ZF's or Yanmar with their many thousands of cone clutch boxes being sold.

It was not until 2008 that Yanmar changed their advice on sailing position with cone clutches, and that is after perhaps selling 50X or more the number of cone clutch gears when compared to the JS's.

I would try and email someone at ZF and tell them what you have and get a better assessment than what Westerbeke, and their distributors, have given you.


P.S. That box does NOT use ATF so be careful with that. I have seen some folks put ATF in there and they were told to do this by their engine installer....

 

[prroots]

Proots,

Your BW-7, I believe, is a cone clutch gear box that is similar in design to a Kanzaki/Yanmar box and not similar to a typical Hurth/ZF box that uses clutch plates. I think the only engines they were used on were some Bukh's and a few Westerbeke models. The BW-6 I know is a cone.

They were built by a Spanish subsidiary of ZF called INDUSTRIAS SUBSIDIARIAS AVIACION SA but are not Hurth's..

With most cone clutches neutral is preferred and the manual states this. I, like you, would strongly question that "forward" will not damage this box.

Yanmar/Kanzaki go so far as to specifically prohibit locking it in any gear while sailing and suggest a shaft brake if locking is desired. Their boxes are also cone clutches. I suspect Westerbeke knows little about what will harm this box having sold so few of them compared to the Hurth/ZF's or Yanmar with their many thousands of cone clutch boxes being sold.

It was not until 2008 that Yanmar changed their advice on sailing position with cone clutches, and that is after perhaps selling 50X or more the number of cone clutch gears when compared to the JS's.

I would try and email someone at ZF and tell them what you have and get a better assessment than what Westerbeke, and their distributors, have given you.


P.S. That box does NOT use ATF so be careful with that. I have seen some folks put ATF in there and they were told to do this by their engine installer....

Thanks as usual for the very comprehensive response. Our transmission says INVERSOR MARINO on it. Wonder if that's the same company you speak of. I will try to communicate directly with ZF. I have tried already to find a contact, but so far have not found one. In the meantime we'll stick with Neutral. By the way, the nameplate says BW-7, but the manual says JS. Not sure if that matters. Yes, the manual does call for SAE 20 or 30 weight oil so we plan to stick with 30 for the more Southern climates.
Pete

 

[prroots]

Just received this via email from the man who has disassembled and diagnosed our transmission prior to our finding a refurbished one from Westerbeke. We sent him a link to this discussion for his reference:

Your BW7 trans uses clutch plates, not a cone clutch, the BW3, & BW6 do use a cone clutch!!! I have included a breakdown of your trans. Also I have sent you a page from a Hurth HBW manual, which is now ZF Marine. The Hurth & BW7 have different parts, but are designed the same. I was aware of a company in Spain, but could not find any info ( this was a long time ago ). I can give you the phone to ZF marine, they may have that information?
ZFmarine--954-441-4068---Bill Liptak
Hope this helps a little?

The attachment referenced above includes the following:

Rotation of the propeller without load 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 battery), will have no detrimental effects on the gearbox.

Important
When the boat is sailing (engine stopped), the gear lever must be in zero position. Never put the gear lever in the position corresponding to the direction of travel of the boat.

Locking of the propeller shaft by an additional brake is not required; use the gear lever position opposite your direction of travel for this purpose.

Comments appreciated.
Pete

 

[prroots]

Here is a photo of the transmission nameplate
Pete

 

[Maine Sail]

Just received this via email from the man who has disassembled and diagnosed our transmission prior to our finding a refurbished one from Westerbeke. We sent him a link to this discussion for his reference:
The attachment referenced above includes the following:Comments appreciated.
Pete

Great info for future reference!

I was basing my assessment of the BW-7 on the BW-6 and the housings look the same so figured it too was a cone.

If it is plates, like the Hurth, then leaving it in forward will certainly kill it. Pretty sad that Westerbeke doesn't know more and actually advises forward gear for sailing....

Can your guy get some pics of inside the gear box? The only JS boxes I have ever seen apart were cones.

 

[prroots]

Thanks for the feedback. We don't have pictures, but I have requested the manual for the BW-7 from ZF which may help resolve the contradictions. I do have an exploded diagram that I received from the above referenced source (see attachment). Not sure if this is from the actual transmission or just one similar.
Pete

 

[prroots]

We just received a reply from ZF that states the shaft should be locked by placing the gear in Reverse (per the attached document).
Pete

 

[Maine Sail]

Thanks for the feedback. We don't have pictures, but I have requested the manual for the BW-7 from ZF which may help resolve the contradictions. I do have an exploded diagram that I received from the above referenced source (see attachment). Not sure if this is from the actual transmission or just one similar.
Pete

That looks like the BW-7 and those are definitely clutch plates not a cone like the BW-6 has. So Westerbeke's information is incorrect as it applies to the BW-7 and it should be in neutral or reverse. You will probably do damage leaving that gear in forward and going by Westerbeke's advise. I would be curious to see what they say after you present them with ZF's response....

 

[prroots]

That looks like the BW-7 and those are definitely clutch plates not a cone like the BW-6 has. So Westerbeke's information is incorrect as it applies to the BW-7 and it should be in neutral or reverse. You will probably do damage leaving that gear in forward and going by Westerbeke's advise. I would be curious to see what they say after you present them with ZF's response....

Thanks. Westerbeke has diplomatically suggested that there is no further need to communicate with them. They first recommended that I consult with my local Westerbeke dealer and then when I report back the contradictory findings they refuse to acknowledge much less apologize. Seems they are a bit short of PR skills

At this point I am still not absolutely convinced who is correct. In Westerbeke's favor they have produced a manual which refers to the JS and BW transmission and certainly the picture and other specs contained therein seems accurate (see excerpt attachment). I really can't figure out why their local dealer, my experienced transmission shop, and the factory all state otherwise. Also, if in error why was it not caught and corrected after at least 10 years? It's a serious mystery to me?

Are there ways from first principles to evaluate which gear to lock it in while sailing?
Pete

 

[Gunni]

If it is a hydraulic clutch transmission you sail with it in neutral. You have a hydraulic clutch transmission. You will, as a result have the ongoing rumble of a rotating propeller and shaft which is why so many Beneteau owners put a feathering prop on their boat - it stops the rotation noise, honors the transmission requirements, and decreases prop drag.

 

[Maine Sail]

If it is a hydraulic clutch transmission you sail with it in neutral. You have a hydraulic clutch transmission. You will, as a result have the ongoing rumble of a rotating propeller and shaft which is why so many Beneteau owners put a feathering prop on their boat - it stops the rotation noise, honors the transmission requirements, and decreases prop drag.

Gunni,

Can you please expand on this or send us to some data or manufacturer information that that support that neutral is a must on Hurth/ZF clutch plate boxes?

That exploded diagram is very, very similar in design to the Hurth HBW series which ZF says to lock in the position opposite of travel or allow it to free wheel, either way is fine.

Yanmar insists on neutral with their cone clutch & plate gear boxes but Hurth/ZF & the BW-7 JS, according to ZF, say locking in reverse is fine. I suspect Westerbeke had a typo on "leave in forward is fine" and now won't own up to it?

ZF seems pretty positive on reverse or neutral for the BW-7..

With the Hurth clutch plate type boxes, specifically the HBW's, leaving them in forward, or same direction of travel, can cause the plates to wear on each other as it does not completely stop the shaft or gears from spinning. Reverse stops the gear from turning. This grinding of the plates in forward puts metallic bits into the ATF or lube oil which then finds it's way to the thrust bearing and wears it out eventually causing the HBW's to slip..

Here's an exploded diagram of the Hurth HBW series:
http://www.marinetransmissions.com/manuals/hurth/hurth_internal.html

And the JS BW-7
http://forums.sbo.sailboatowners.com/attachment.php?attachmentid=44628&d=1318946293

 

[Gunni]

Yanmar insists on neutral for all of their hydraulic transmissions the cone variety and the wet-disc variety. And not all Kanzaki transmissions are cone type BTW.

The rationale is the same - with the engine stopped and the transmission in gear, a loaded propshaft (prop not free-wheeling) will have the transmission slip surfaces (hydraulic friction surfaces) slipping/wearing and eventually locking up. The stopped engine cannot be rotated by the nominal force of the in-gear propshaft and the transmission slip surfaces take the energy as friction. Shifting to reverse would not change that.

Moving the transmission to neutral disconnects the transmission gears from the stopped engine drive shaft and allows the hydraulic/wet plate surfaces to rotate without load or wear.

One of the transmission guys at Mack Boring stepped me through the logic. Hydraulic and wet plate transmissions should never be loaded from the output side while locked down on the input side (engine). He said they learned this by seeing the same transmission failure over and over in marine applications. I guess they didn't anticipate what all us old dogs, who have always dropped our transmissions in gear to stop the prop, would do to these modern transmissions.

 

[Maine Sail]

Yanmar insists on neutral for all of their hydraulic transmissions the cone variety and the wet-disc variety. And not all Kanzaki transmissions are cone type BTW.

The rationale is the same - with the engine stopped and the transmission in gear, a loaded propshaft (prop not free-wheeling) will have the transmission slip surfaces (hydraulic friction surfaces) slipping/wearing and eventually locking up. The stopped engine cannot be rotated by the nominal force of the in-gear propshaft and the transmission slip surfaces take the energy as friction. Shifting to reverse would not change that.

Moving the transmission to neutral disconnects the transmission gears from the stopped engine drive shaft and allows the hydraulic/wet plate surfaces to rotate without load or wear.

One of the transmission guys at Mack Boring stepped me through the logic. Hydraulic and wet plate transmissions should never be loaded from the output side while locked down on the input side (engine). He said they learned this by seeing the same transmission failure over and over in marine applications. I guess they didn't anticipate what all us old dogs, who have always dropped our transmissions in gear to stop the prop, would do to these modern transmissions.

And yet Hurth/ZF strongly disagree with that for their gears. Perhaps the Kanzaki's are built slightly differently than the Hurth/ZF boxes.

Hurth/ZF have made it very clear that locking in reverse with their clutch plate boxes is perfectly fine. I have never seen a Hurth "slip" when locked in reverse. In fact I regularly turn engines over when working on couplings or props without causing the gear to ever "slip". Just did this Monday while replacing a shaft and coupling on a Westerbeke with a Hurth HBW 100. Sometimes the strap wrench is not enough to hold the shaft while trying to remove a prop nut or coupling bolt, or tighten one.

Our Hurth/ZF is almost always locked in reverse, unless I want a little more speed, and the boat has over 25,000 nm miles and 3200 engine hours on her since the engine replacement. Gear box performs flawlessly and the ATF is always pink when changed with zero signs of clutch plate slippage residue. This box has never been re-built nor needs or needed it..

I don't think it is fair to apply Yanmar / Kanzaki logic to Hurth/ZF gear boxes when Hurth/ZF have, and still do, express different operation techniques than Yanmar/Kanzaki..

And their most recent statement:

Hurth/ZF Sailing Gear Position.pdf

 

[Stu Jackson]

I know you've talked to Westerbeke, but have you talked to Joe Joyce? I suggest you try to get to him, he knows his stuff.

 

[prroots]

I know you've talked to Westerbeke, but have you talked to Joe Joyce? I suggest you try to get to him, he knows his stuff.

Coincidentally, I just forwarded him the email received from ZF stating that one locks the shaft by placing the transmission in Reverse. Prior to this I had asked Beneteau the question who in turn forwarded the request to Westerbeke. Joe Joyce responded by simply attaching the manual which states you lock the shaft by placing the transmission in Forward.
Pete

 

[prroots]

If it is a hydraulic clutch transmission you sail with it in neutral. You have a hydraulic clutch transmission. You will, as a result have the ongoing rumble of a rotating propeller and shaft which is why so many Beneteau owners put a feathering prop on their boat - it stops the rotation noise, honors the transmission requirements, and decreases prop drag.

The transmission shop that disassembled and diagnosed the failure of our ZF model BW-7 transmission has confirmed that it's a mechanical not a hydraulic transmission.
Pete

 

[Gunni]

The transmission shop that disassembled and diagnosed the failure of our ZF model BW-7 transmission has confirmed that it's a mechanical not a hydraulic transmission.
Pete

To a transmission mechanic a wet-plate clutch transmission isn't a "hydraulic transmission", but to an old all-gear transmission user it is, it uses an oil-bathed clutch surface that I refer to as hydraulic. There are wet clutches with slip-friction surfaces, designed to slip, all through the drive train. And wet plates don't like a prop in gear, rotating the clutches. Maine Sail says you can lock down your ZF in reverse and not damage the plates. I don't understand how that works. I run a Kanzaki wet plate transmission and it MUST be parked in neutral, or you will destroy the plates. I would ask ZF how placing their transmission in reverse "locks" the transmission. It may be that the PO was an old-timer who thought it was fine to park the transmission in forward (not reverse). Or the boat was a charter...