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Old 07-06-2015, 09:29   #16
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Re: Weird Clutch Problem

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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?
That sounds plausible, at least to my virgin ears which know nothing about marine transmissions.

No, I never motored at such low RPM and probably shouldn't have done it. I was sleeping and the guy on watch didn't think he should shut down the engine which I had left on, although the wind had come up a little. So probably no power was being taken from the engine and maybe that let the clutches slip, if they work on the basis of jamming from power from the engine. That could be just it.
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Old 07-06-2015, 11:29   #17
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Re: Weird Clutch Problem

Makes sense to me.

The engine and prop push against the water, forcing the cone and drive gear together. As sail power increased relative to decreasing tranfer of prop thrust (at low power already) effectively decreases the coupling force at the cone. Then some slippage occurs.

My guess is no real harm occurred.
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Old 07-06-2015, 11:43   #18
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Re: Weird Clutch Problem

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Originally Posted by Dockhead View Post
That sounds plausible, at least to my virgin ears which know nothing about marine transmissions.

No, I never motored at such low RPM and probably shouldn't have done it. I was sleeping and the guy on watch didn't think he should shut down the engine which I had left on, although the wind had come up a little. So probably no power was being taken from the engine and maybe that let the clutches slip, if they work on the basis of jamming from power from the engine. That could be just it.
Indeed it could. Rereading my earlier post I may have sounded more pessimistic than I intended. It was merely one of multiple scenarios. Four Winds cone slip scenario is very possibly correct.
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Old 07-06-2015, 11:48   #19
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Re: Weird Clutch Problem

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Originally Posted by Muckle Flugga View Post
Indeed it could. Rereading my earlier post I may have sounded more pessimistic than I intended. It was merely one of multiple scenarios. Four Winds cone slip scenario is very possibly correct.
Let's hope so. But your "pessimistic" post was also extremely informative; thanks for that.
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Old 07-06-2015, 12:27   #20
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Weird Clutch Problem

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stop in neutral - **** to close the Gori

Oops - sorry for typo ! Should be 'shift' to close Gori ! 😳
More haste, less speed

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Old 05-07-2015, 10:15   #21
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Re: Weird Clutch Problem

The advice given by four winds is correct ! when motor sailing the wedging/application effect caused by the prop shaft becomes less and less as engine speed goes down or boat speed up to the point slippage occurs
When motor sailing in my own boat as the wind picks up or engine rpm goes down I feel the trans disconnect and reconnect on waves or wind puffs this means its time to increase rpms or place shift lever in neutral
Point is there needs to be more pressure from the engine to apply the clutches properly
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Old 02-03-2016, 03:38   #22
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Re: Weird Clutch Problem

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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.
Old thread I know but I came across it because I am having similar not the same weird noises while motorsailing - subject of a new thread however.

Regarding the slight overfilling issue, I don't think this would have caused your slippling. I suspect (but don't know for sure) that it was coincidental the slipping stopped at the same time as correcting the oil level.

The slipping may have been due to other effects and caused some slight polishing of the cones which later led to the events you describe in this thread.

However if anyone can explain to me how slight overfilling can cause slipping, I would be very grateful!
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Old 02-03-2016, 03:40   #23
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Re: Weird Clutch Problem

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Old thread I know but I came across it because I am having similar not the same weird noises while motorsailing - subject of a new thread however.

Regarding the slight overfilling issue, I don't think this would have caused your slippling. I suspect (but don't know for sure) that it was coincidental the slipping stopped at the same time as correcting the oil level.

The slipping may have been due to other effects and caused some slight polishing of the cones which later led to the events you describe in this thread.

However if anyone can explain to me how slight overfilling can cause slipping, I would be very grateful!
All I can say is that it was slipping quite a lot, and this slipping INSTANTLY stopped when I corrected the level.

I can't explain it, but sure doesn't sound like a coincidence to me.

The transmission has been working fine ever since -- several hundred hours later.
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Old 02-03-2016, 04:56   #24
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Re: Weird Clutch Problem

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All I can say is that it was slipping quite a lot, and this slipping INSTANTLY stopped when I corrected the level.

I can't explain it, but sure doesn't sound like a coincidence to me.

The transmission has been working fine ever since -- several hundred hours later.
I have to agree that is doesn't sound like a coincidence!

Can you recall by much it was overfilled either by quantity or dipstick measurement?
Did you simply remove the excess or change the oil at the same?
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Old 02-03-2016, 08:37   #25
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Re: Weird Clutch Problem

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Originally Posted by Wotname View Post
I have to agree that is doesn't sound like a coincidence!

Can you recall by much it was overfilled either by quantity or dipstick measurement?
Did you simply remove the excess or change the oil at the same?
I don't know how much it was overfilled. I used the oil suction pump to remove it little by little until it was at the right level.

I had changed the oil and made wrong assumptions about how to check the level. Yanmar have crazy oil level procedures.

Did you know that with their engines, you are supposed to check them right after running and shutting down? NOT after letting the oil drain down like with normal engines
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Old 02-03-2016, 16:03   #26
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Re: Weird Clutch Problem

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........ Yanmar have crazy oil level procedures.

Did you know that with their engines, you are supposed to check them right after running and shutting down? NOT after letting the oil drain down like with normal engines
Ain't that the truth. I've almost given up trying to understand Yanmar directions on engine operation.

Contrary to your Yanmar advice, my 2GM20 operation manual clearly states in para 4.3.1 (1).7 to wait ten minutes after shutting down the engine before checking engine oil level.

As for gearbox levels, for years I have read that the dipstick must NOT be screwed in when measuring the gear oil level. My manual states in para 3.2.3.2 to fully insert the dipstick to check the level. Presumably fully insert includes screwing it down...

BUT the preceding para for engine oil ( para 3.2.2.2) has exactly the same wording which tends to make me think the previous engine oil para was copied and pasted to the gear oil para and the thus gear oil instuctions contain an error.

Now days I extract as much gear oil as possible with the pump and simply add a measured 280 cc of oil. The book states the capacity is 300cc and I am guessing there is 20 cc of old oil remaining in the box. The oil level on the dipstick is close to the mark when NOT screwed in but who knowes what is correct - the operation manual or what
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Old 02-03-2016, 16:18   #27
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Weird Clutch Problem

Overfilling oil can get the level up into the moving parts, this can beat the oil into a foam, and if it is used for hydraulic clutch packs or bands like an automatic transmission of a car for instance, this foam has air and is compressible and clutches will slip.
Overfilling the oil level on an engine can do something similar in that it will beat air into the oil, causing foam and a loss of oil pressure, of course at about that point the foam will be coming out of the crankcase breather which is usually connected to the intake, and of course the engine will smoke profusely, and nobody can ignore that.

Lots of high performance engines in days past had windgate trays connected to the main bearing caps, this tray kept oil away from the crankshaft which kept it from being beaten and saved a bit of horsepower or course.


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