Weird Clutch Problem

[Dockhead]

We had a long, slow and very pleasant passage across the Baltic to Estonia, about 170 miles. Downwind in light wind, just ghosting along sometimes. This time of year at this latitude, theres not any real night. Just a long dusk turning back into dawn before any real darkness occurs, making night passages a particular joy. This part of the Baltic, outside the Deep Water Route, seems like a vast emptiness. No traffic, no ships, no boats, just empty sea.

We did some motorsailing when the wind dropped below about 8 knots true, sometimes at very low RPM. After a few hours motorsailing at 1000 rpm, there was a cyclical squeaking sound. Drove me crazy. Dove on the lazarette to check the pilot pump (low fluid?). Finally realized it was the shaft turning. Started the engine, shifted into reverse, shut it down again. Still turning. Then put it in forward and ran it hard, 3000 rpm, for a few minutes. Shut it down again and since then, all normal.

What was that?

[d4raffy]

This sounds too easy - maybe I have missed something ?
Prop turning shaft whilst sailing ?

On my Yanmar, I have to sometimes put it into reverse (no engine running) to close the Gori down - then back to neutral - shaft stops spinning.



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[nigel1]

No idea, but does not sound right if shaft turned while the gearbox was set to astern.

Bears more investigation, try again and see if you can turn the shaft by hand while gear box in astern position. If it turns,sounds like a gear box problem. Trust gear box oil level is OK.

[Dockhead]

Originally Posted by d4raffy

This sounds too easy - maybe I have missed something ?
Prop turning shaft whilst sailing ?

On my Yanmar, I have to sometimes put it into reverse (no engine running) to close the Gori down - then back to neutral - shaft stops spinning.

As I wrote --- shaft was turning with the gearbox in gear. Both forward and reverse. Until I ran the engine up in forward for a while. Then everything back to normal.

And no problems since, several hundred miles later.

Still puzzled.

[Dockhead]

Originally Posted by nigel1

No idea, but does not sound right if shaft turned while the gearbox was set to astern.

Bears more investigation, try again and see if you can turn the shaft by hand while gear box in astern position. If it turns,sounds like a gear box problem. Trust gear box oil level is OK.

It turned in both ahead and astern.

I did have a problem with the clutch slipping, last year, as a result of slightly overfilled oil. Disappeared when I corrected the oil level. But this was different -- clutch slipped while motoring in gear.

[Kenomac]

Do you have a feathering prop like a Maxprop? If so, you need to put the boat in reverse, give it some throttle to reverse feather the prop, then shut the engine off while in reverse, in order to stop the shaft from turning. This will make the prop blades face directly forward. If you have a Maxprop, this is how the instruction manual states how to do it.

[LeaseOnLife]

Originally Posted by Kenomac

Do you have a feathering prop like a Maxprop? If so, you need to put the boat in reverse, give it some throttle to reverse feather the prop, then shut the engine off while in reverse, in order to stop the shaft from turning. This will make the prop blades face directly forward. If you have a Maxprop, this is how the instruction manual states how to do it.

You must have a different MaxProp than mine. For my MaxProp VP the manual says:

PROPELLER USE:
The Max-prop works automatically. By putting the engine in gear the blades will engage in either forward or reverse. The best way to feather the propeller is:
• Power at 2 to 3 knots in forward.
• Kill the engine while still engaged in forward.
• When the engine has stopped, if the shaft is still spinning engage the transmission
in reverse to stop the freewheeling.
You can check to see if the propeller is feathered or not by taking the engine out of
gear. If the propeller is not feathered the shaft will freewheel like with a fixed blade
propeller. In that case start the engine again and repeat the three steps. If your propeller has been greased properly it will feather in a fraction of a second as soon as you stop the shaft from freewheeling. Once the prop is feathered, you can either leave the transmission in gear or out of gear, it does not matter.
DO NOT kill the engine while in reverse. In this case the blades will be in the reverse position and will not feather. You can actually use this feature to drive a shaft alternator

[Kenomac]

Originally Posted by LeaseOnLife

You must have a different MaxProp than mine. For my MaxProp VP the manual says:

Thanks, I'll try that. I'd understood it differently. All I knew after reading the manual is that the reverse gear killed the free wheeling.

Ken

[Dockhead]

You're both right. Or if one of you is wrong, there is no concrete information about it.

My Moody manual says to kill the engine while motoring in forward.

My Autoprop manual says to shift to reverse.

I follow the Moody manual practice and have never had any problems until now.

[d4raffy]

Originally Posted by Dockhead

As I wrote --- shaft was turning with the gearbox in gear. Both forward and reverse.

OK - not sure I read that - I had assumed you always stop the engine (after going fwd or rev) in neutral. Isn't stopping in gear bad in some way for the engine ?? Maybe my wrong assumption.

Like a car - stop in neutral - shift into gear for parked considerations - hills !

Same with me boat - stop in neutral - **** to close the Gori if the shaft spins - then back to neutral.

But I suppose folks with non feathering props always leave it in gear ?


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[Muckle Flugga]

Originally Posted by Dockhead

We had a long, slow and very pleasant passage across the Baltic to Estonia, about 170 miles. Downwind in light wind, just ghosting along sometimes. This time of year at this latitude, theres not any real night. Just a long dusk turning back into dawn before any real darkness occurs, making night passages a particular joy. This part of the Baltic, outside the Deep Water Route, seems like a vast emptiness. No traffic, no ships, no boats, just empty sea.

We did some motorsailing when the wind dropped below about 8 knots true, sometimes at very low RPM. After a few hours motorsailing at 1000 rpm, there was a cyclical squeaking sound. Drove me crazy. Dove on the lazarette to check the pilot pump (low fluid?). Finally realized it was the shaft turning. Started the engine, shifted into reverse, shut it down again. Still turning. Then put it in forward and ran it hard, 3000 rpm, for a few minutes. Shut it down again and since then, all normal.

What was that?

A little unclear about this. Were you motorsailing or not? Normally when I motorsail my engine will be on…

And, did you note whether while engaged and running astern the shaft and prop were powered? This should have been obvious. It would be weird indeed if the shaft were engaged positively with power through the prop, but then freewheeled when simply shut down. Uncharacteristically a bit unclear there, Dockhead. Surprising for one normally so crystal and precise.

In any case it sounds rather like you are seeing the beginning of a failure to engage in the gearbox, which is likely due to a worn clutch selector fork.

What is the make and model? Hurth ZF?

In any case, if an older model box and the problem is a worn fork, you are likely looking at total failure in the nearish future. One thing that you will begin to notice if so, is the box slipping out of gear suddenly on a high/redline load. A box can be rebuilt… but it is likely more cost effective just to pull it out and bolt in a new one. If you are in the Baltic and it is a ZF, then sourcing one should be a doddle. ZF has been careful about matching their new models to the old models for 1 to 1 exchangeability so if ZF likely good. Depending on your access the actual mechanical work to replace is pretty easy and with a good spanner and socket set you should be able to do it yourself no issues. If you do, don't forget to check the damper plate inside the bell housing while you're at it. A very common reason for major drive failure is a wrecked plate and very few people open the bell housing to check this consumable (and generally very inexpensive) and vital part. Also an easy job to replace once you've popped the housing. My guess if you have selector issues and slippage? Your damper plate springs or buffers will be in pieces at the bottom of the housing and you will have been hard engaging the gears with no damping…

Anyhow, it may not be severe, but the above are all well possible.

[Dockhead]

Originally Posted by Muckle Flugga

A little unclear about this. Were you motorsailing or not? Normally when I motorsail my engine will be on…

And, did you note whether while engaged and running astern the shaft and prop were powered? This should have been obvious. It would be weird indeed if the shaft were engaged positively with power through the prop, but then freewheeled when simply shut down. Uncharacteristically a bit unclear there, Dockhead. Surprising for one normally so crystal and precise.

In any case it sounds rather like you are seeing the beginning of a failure to engage in the gearbox, which is likely due to a worn clutch selector fork.

What is the make and model? Hurth ZF?

In any case, if an older model box and the problem is a worn fork, you are likely looking at total failure in the nearish future. One thing that you will begin to notice if so, is the box slipping out of gear suddenly on a high/redline load. A box can be rebuilt… but it is likely more cost effective just to pull it out and bolt in a new one. If you are in the Baltic and it is a ZF, then sourcing one should be a doddle. ZF has been careful about matching their new models to the old models for 1 to 1 exchangeability so if ZF likely good. Depending on your access the actual mechanical work to replace is pretty easy and with a good spanner and socket set you should be able to do it yourself no issues. If you do, don't forget to check the damper plate inside the bell housing while you're at it. A very common reason for major drive failure is a wrecked plate and very few people open the bell housing to check this consumable (and generally very inexpensive) and vital part. Also an easy job to replace once you've popped the housing. My guess if you have selector issues and slippage? Your damper plate springs or buffers will be in pieces at the bottom of the housing and you will have been hard engaging the gears with no damping…

Anyhow, it may not be severe, but the above are all well possible.

Thanks -- a goldmine of valuable info for those of us who don't understand marine gearboxes (like a lot of people on here, my knowledge of mechanical systems comes mainly from experience working on cars).

We motorsailed for some hours at very low RPM, then the squeaking sound and turning shaft came after we shut the engine down. Wouldn't stop turning after I tried reverse. But it did stop turning after I ran the engine up to 2000 RPM or so in forward and ran it like that for a few minutes. Since then, it's been normal.

The gearbox (a Kanzaki, I think, not ZF -- standard Yanmar), like the main engine, only has about 2000 hours on it, so I sure hope there isn't any major failure. It's now working fine, shifting into gear the same as it always did, with a mild clunk as always.

The only other trouble I ever had with it was last year when it was slipping due to overfilling. The oil smelt fine and the problem disappeared when I corrected the oil level, so I think I caught it before doing any damage.

But the question remains -- why? And how? Can anyone explain how these clutches work? I also don't understand at all why slight overfilling would cause them to slip -- seems bizarre to me.

[Kenomac]

I doubt is the gearbox, sounds like a feathering prop issue. You did exactly what the Maxprop manual stated to do when the freewheeling stopped.

[monte]

Our saildrive with flexifold prop occasionally doesn't fold properly. We hear a slight whine as it turns the shaft in the sail drive. We always leave it in neutral. Slipping into forward gear for a few seconds while sailing is usually enough to fold the prop and stop it turning in neutral.

[four winds]

My Kanzaki uses cone clutches instead of disc. Not sure for your model.

One cone for forward and one for reverse. The surface of the "cone" has shallow oil grooves to provide a thin film lube for the mating surface. This surface is pressed hard against the corresponding surface of the forward or reverse drive gears by the power delivered from the engine. More power, mating surfaces pressed together with more force.

So here's my guess. Hours of low power motoring had a glazing effect on the cone friction surfaces. Simar to rings when charging with no load.

Motoring hard ahead for a while cleaned up those surfaces and all is back to normal.

Ever motored so low rpm for so long before?