What does your ATF oil look like when you change it ?

[perchance]

Originally Posted by motion30

My question no cooler? I cant remember seeing a boat without a trans cooler If I had those failures I would have installed a cooler long ago Seems simple am I missing something here?

An oil cooler will not help much if the clutch is slipping due to under sizing. These mechanical clutches rely on spring tension to keep them locked up and can only exert so much force.

[Astrid]

The manual also goes on to say that with the engine off, the prop may freewheel without damage to the transmission:

The propeller may turn owing to the
effect of the current when the engine
is off and the craft is sailing, or when it
is tugged or anchored. This represents
no danger for the transmission.

So you have your choice--if the shaft must be locked for work on the transmission or for feathering props, then lock by moving the gearshift in accordance with the manual; otherwise, with a fixed prop, it will not harm the transmission to let it freewheel.

Following is a link for the online manual:

http://www.bukh-bremen.de/files/346/...0.01.0006f.pdf

[Jim Cate]

Originally Posted by perchance

An oil cooler will not help much if the clutch is slipping due to under sizing. These mechanical clutches rely on spring tension to keep them locked up and can only exert so much force.

Actually, I believe that ZF trannies use balls rolling up inclined ramps between the plates to force them together, not springs.

But, the amount of HP that they can safely carry is related to RPM -- higher RPM, more power. So, it's really a matter of how much torque they can handle. A careful inspection of the engines HP vs RPM curve related to the ZF specs might reveal that you are over the limit.

Cheers,

Jim

[sgtPluck]

Jim Cate, I wondered about that, and it is something I need to check with ZF. i.e. is there a risk of the clutch not being properly engaged if the rpms are too low (not enough centrifugal force), thereby possibly slipping/burning the clutch.
Although that was a consideration I was mindful of, and did not leave it in idle (850 rpm) forward for any long period of time.

I couldn't find my engine specs, and I'm really not sure if I'm reading the ZF ones correctly...
http://www.marinepartsexpress.com/pr...07/ZF_10_M.pdf

One interpretation of the details in the specs would suggest (if the ratings are for input power) that I could be overpowered in the continuous duty rating. But that doesn't align with the summary specs which suggest 37hp for continuous duty.

[S/V Antares]

If you have a ZF you might want to check out "Temp Dots" which are a small strip that you stick on the gearbox. It will show the highest temp seen.
Palmer Wahl Temp-Plate Temperature Recording Labels

[Jim Cate]

Originally Posted by sgtPluck

Jim Cate, I wondered about that, and it is something I need to check with ZF. i.e. is there a risk of the clutch not being properly engaged if the rpms are too low (not enough centrifugal force), thereby possibly slipping/burning the clutch.
Although that was a consideration I was mindful of, and did not leave it in idle (850 rpm) forward for any long period of time.

I couldn't find my engine specs, and I'm really not sure if I'm reading the ZF ones correctly...
http://www.marinepartsexpress.com/pr...07/ZF_10_M.pdf

One interpretation of the details in the specs would suggest (if the ratings are for input power) that I could be overpowered in the continuous duty rating. But that doesn't align with the summary specs which suggest 37hp for continuous duty.

SgtP, it isn't a matter of centrifugal engagement, so I don't think that idling forward is an issue. It's a bit hard to describe, but the clutches are forced together by the balls rolling up ramps on the discs, driven by differential rotation. As they roll up they squeeze the plates together, and that's what engages the drive. Essentially, the more torque that is applied, the harder the plates are squeezed together. Poorly worded, I fear...

At any rate, you will need to find your hp vs rpm curve, and find out what HP is being supplied at your various cruising and max speeds. Then compare those powers with the limits shown in the ZF manual for the same RPMs. For instance, I believe that the 37 bhp continuous is at 5000 rpm (from memory of an earlier posting), and the lower the RPMs the lower the rated HP is. I'm 7000 miles away from our boat and my copies of the ZF10 manual so I can't check them for you. It is possible that you are exceeding the ratings, but offhand I doubt that this is the problem.

Hope that the "expert" can help you out.

Cheers,

Jim

[sgtPluck]

Interesting, thanks.

The ZF 10M Specs are here:
http://www.marinepartsexpress.com/pr...07/ZF_10_M.pdf

The M-25xpb is here:
http://www.marinedieseldirect.com/re...sal/m25xpb.pdf

It looks like at 2400 rpm (I never go above that, and on this latest gear have not gone above 2200) it seems like it's around 20hp. If I'm reading it correctly the ZF10m should be rated for around 24hp at that RPM (at continuous duty, which I use as worst case scenario)

It does look like it might cut it a tad close, because they also say that in the small print that you should reduce the power factor by a 1.15 ratio for a 3 cylinder engine, although I don't know what margins would be normal to leave in this kind of system.

My boat is heavy for its size and has a lot of wetted area, not sure if these are considerations that might narrow the margin further.

[Jim Cate]

G'Day again SgtP,

There's the data! And it looks like your reading is correct. You are just about on the limit when you stick in the 3 cylinder correction, and certainly not far above it. And, in truth, I don't think motoring down the ICW for a couple of days meets their criteria for heavy duty... so I don't think that this is the problem with your installation.

OH, one question: you do have the 2:1 reduction, not the 2.8:1, don't you?
IF it is the 2.8:1 then you are above their limits I think.

Also, the weight and wetted area of your boat do not enter into the equation here. The engine and tranny only know that it is transmitting 20 HP to the prop at some RPM, not what the boat is doing.

Cheers,

Jim

[Boracay]

Another point that you may care to double check. On my ZF63 the manual says to check the oil level when oil is warm, just after stopping the engine.

I did not find a big difference either way.

I also have a filter that needs to be changed after 50 hours initially and every 300 hours after that. This is from memory (unreliable) as the manual's on the boat.

Another random thought: If you're changing the transmission again I'd consider sending the coupling off to the the machine shop and getting them to check the whole thing for straightness. They might even be able to machine a few marks on it to help with alignment...

If the oil is white and its not water then one or more internal components could be trashing themselves.

If it were me I'd be carrying a big container of ATF oil, checking the transmission every time I used it and changing the oil at the slightest hint of trouble.

[sgtPluck]

Gday Jim,
I have the 2.0.4 gear.
The last one that failed I ran quite hard, New York to Florida on the ICW, some motor sailing into rough seas, and one 29 hour stretch when I was becalmed offshore.
But the one I just put in in Georgetown only has 25 hours on it, I sailed most of the way back here and babied the transmission when I was motoring. I only motored in flat seas when I had no wind, and didn't go over 2200 rpm and mostly less than that, yet still - burnt oil apparently due to clutch slippage. My prop was a bit rough surfaced, but not terrible.

Boracay, I've been checking the oil warm and cold. I was worried that I might be putting too much or too little in. The dipstick is quite hard to read. But I've been very careful. I've changed the oil twice already, in 25 hours. Nassau was the last time, maybe 10 hours of gear use ago, and the oil is purple/opaque already. I have not used it since I changed the pitch on my prop. I'll check it again in a few hours of use and see what it looks like.

I'm stumped. Maybe the tiniest bit of misalignment is enough to push it over the edge. But I've tested it myself, and paid two mechanics to look at it, both of whom said it looked perfect.

[Maine Sail]

Originally Posted by sgtPluck

Thanks Target9000, I will double and triple-check the alignment to be sure.

The engine is a Universal 25XPB. The specs for the ZF10 say it can handle 37hp continuous duty. But the detailed ratings are confusing, they say something about max rated power at 24hp at 2300rpm. I wasn't sure if that meant output or input power, someone told me it meant input.

http://www.marinepartsexpress.com/pr...07/ZF_10_M.pdf

Anecdotally, someone at ZF and someone at Foley said to me that they thought these gears were really meant for light in and out of the harbour duty.

Please be careful. If you need Hurth/ZF stuff in MA try Hansen Marine.

Originally Posted by sgtPluck

I usually put it in reverse, I did accidentally leave it in forward for a short while.

This is perhaps the worst thing you can do to these boxes. Leaving it in forward allows the plates to slip and shed metallic particles into the lube oil. These boxes are splash lubed, and the 100 only has less than a half a quart, so when the lube is full of metallic bits it becomes abrasive. Abrasive is not good with slightly less than a half quart or ATF.

They also use a bronze thrust washer that takes the load. When the oil is abrasive the thrust washer wears out allowing slipping. Changing the fluid in these on a regular basis is a necessity. I have seen HBW 100's on M-25's go for well over 2500 hours. The 10M takes mostly the same parts and is largely unchanged other than the name change.. Many thousands of Catalina's, lots of Ericson's, Pearson, Cape Dory and others used this exact combination. Many of these have died an untimely death and they are what I'd consider a lightly built box but taken care of they can certainly last.

I explain to all my customers that if you ever leave it in forward, for even a short time while sailing, change the fluid as soon as possible. Use the bottom drain to make sure you get it all. The HBW 100/ZF 10M bottom tap though is not 100% at the dead bottom so you'll want to suck the majority of it out via hose. Getting to the bottom of that box with a suction hose is no easy task..


We have a Hurth V-Drive and she's got 3200 hours on her with zero issues but the fluid is changed at a minimum yearly and always comes out pink. Fluid changes on these cost about $1.50 and take minimal time so there really is little to no excuse. Even if you change the drain washer and dip tube washer your still at less than $4.00 to change this fluid.

This is what thrust washer wear looks like:


And clutch plates that had been slipping:


Everyone I have seen that needed a rebuild did not have clean gear box oil. I suspect this may not be just a coincidence?? What your doing is good, changing the fluid, but I suspect there may be another issue we're missing.?

Can you get your M-25XPB to full rated max RPM?

[sgtPluck]

Thanks Maine Sail,
I did leave this new gear in forward once. I remember kicking myself when I realized, but I don't know how long I had it in forward for. There are no more than 8 hours on it since. I changed the oil yesterday using my suction pump. How much damage can that do?

I was 100 shy of the rated 3000 rpm on my last gear. But that was a 1.79 the first and current gears are 2.04 . I re pitched my prop anyway last week, hoping it might help.

[sgtPluck]

I have a new thought about a potential cause for the burnt oil. I wonder if anyone - in particular anyone with a ZF transmission can chime in on this....

I have noticed that there is a little bit of play in neutral, at the lever on the gear itself and at the shifting lever at the steering pedestal. This is such that the lever on the gear itself may be around .6cm aft (measured at the top of the lever) which is .6cm in the direction of forward gear. I wonder if it is possible that this could cause the plates to touch very slightly, and therefore cause the burned oil that I'm seeing?

Does anyone with a ZF know if their lever has any play, or is it always perfectly at 0 degrees relative to the gear?


thx