Visit our Popular Forums

**Wotname** · 02-03-2016, 03:37

Can anyone please explain the following symptoms?

Motorsailing at normal power for several hours in light variable winds with a reasonably lumpy sea (sevearl swell patterns, some a couple of metres). Boat speed all over the shop due to the confused seas.
Transmission is a Kanzaki KM2P (cone clutch) on a Yanmar 2GM20 with fixed 3 blade prop, composite bearing each end of shaft and a PSS seal.

Suddenly the prop / shaft / transmission starts screeching in a high pitched fashion. Something like a dry wheel bearing or such. Immediately pulled back to neutral and the noise stops. Let it idle for a few minutes in neutral before gingerly engaging forward. All
sounded normal at low power and then slowly advanced to normal power. Ran ok for say a minute or two before a terrible low pitch rumbling grinding noise occured. It sounded like metal being torn apart under rotation. This time, stopped engine for a better investigation!

Oil was normal in colour and quantity.
Shift lever was operating normally and with correct travel.

Found that in neutral, propshaft could be rotated by hand in either direction and felt normal.
No binding or noise.

In astern, prop shaft could be rotated by hand in normal direction and was locked in the other direction. This I believe is normal.

In ahead, prop shaft could be rotated by hand in either direction which lead me to think I have a transmission problem.

Gearbox and coupling felt hot to touch not so hot as to burn, guessing about 40 - 45C. I don't know if this is normal or not!

Then tried rotating the engine (decompressed) with hand crank and prop turned normally (ahead and astern) without any problems or noises. After that excerise, the prop could no longer be turned both ways by hand when selected to ahead. That is, it seemed normal.

Restarted engine and again tried ahead, this time, it seemed OK at low power (1800 rpm), so proceeded for another hour to get to a safe(ish) fair weather anchorage.

After a long look, we could not find anything wrong externally and tried the engine again. This time, all ran well at all power settings although I was not willing to try full power (3400+rpm) for more than a minute as we were a very long way from normal help (like people, phones, roads etc) and the coast had no safe all weather havens.

Since then, we sailed back to safe anchorage (with coms) and used the engine for about an hour at low power and maybe 15- 20 minutes at normal power. No abnormal noises heard.

Still treating it very gently until we can get to a port with repair facilities (ie home

).

Any ideas as what might be the cause?

Transmission cones???
Prop shaft bearing???
Something fouling the prop???

I can't belive it has fixed itself

Blue Stocking · 02-03-2016, 04:39

Possibly sail generated speed exceeded power driven speed, and freed up the trans mission from load ?

sartorst · 02-03-2016, 06:29

Read the weird clutch thread I think you have the same thing happening
My own personal experience when motor sailing has not created high pitch noises but has made some pretty violent rapped jerking in and out of engagement type sound that could be misconstrued as grinding, all of which is normal for a cone type transmission

**Wotname** · 02-03-2016, 15:43

Quote:

Originally Posted by sartorst

Read the weird clutch thread I think you have the same thing happening
My own personal experience when motor sailing has not created high pitch noises but has made some pretty violent rapped jerking in and out of engagement type sound that could be misconstrued as grinding, all of which is normal for a cone type transmission

Yes, I read that thread and I really hope you are right! The grinding / tearing noise could have a violent rapped jerking of engagement. The high pitched noise preceeding it might have been cone slippage as it had a vague slippimg dry bearing sound about it. It certainly rattled me at the time as I have never experienced such noises over the years of motor assisted sailing plus we were in a remote area where the engine performace was going to be more critical than sailing performace.

However I remain concerned until we can get the boat slipped and inspect all the drive systems components from prop nut to engine output shaft. Thanks for your input.

**Wotname** · 03-03-2016, 00:29

Supplementary question:

What are the usual symptoms of the cones slipping (due to wear or whatever) as opposed the prop producing more torque than the engine?

**atoll** · 03-03-2016, 00:48

it sounds like you had something like a plastic bag fouling the prop,causing the oil to heat up which in turn allowed the cone to slip which caused the noise.

the bit of plastic probably floated off when you stopped,and the oil cooled allowing the cone to function normally again.

I have also heard from second hand car salesmen that a hand full of sawdust in the gearbox works well for noisy transmissions.................

sartorst · 03-03-2016, 04:39

Quote:

Originally Posted by Wotname

Supplementary question:

What are the usual symptoms of the cones slipping (due to wear or whatever) as opposed the prop producing more torque than the engine?

jerking and slipping or no engagement at all under load

Xthewater · 03-03-2016, 08:27

I may be off base here but my suspicion as a maybe was the cutlass bearing became dry? Not sure what meant by composite so like I said I'm probably way off here.

davewtsnape · 03-03-2016, 10:11

I have had the ame problem just motoring off and on for five years in my Moody 37. Changed the gearbox no difference. Assume it is cavitation of the prop. Will change the cutlass bearing this year and see what happens.

**Wotname** · 03-03-2016, 13:56

Quote:

Originally Posted by Blue Stocking

Possibly sail generated speed exceeded power driven speed, and freed up the trans mission from load ?

Quote:

Originally Posted by sartorst

Read the weird clutch thread I think you have the same thing happening
My own personal experience when motor sailing has not created high pitch noises but has made some pretty violent rapped jerking in and out of engagement type sound that could be misconstrued as grinding, all of which is normal for a cone type transmission

If this was the cause of the abnormal noises, then it would seem that dropping the sails and just motoring may be a solution until stronger winds return???

sartorst · 03-03-2016, 14:11

In a cone type transmission which is the most common,simple, cheaper type
when the shift hub/cone is moved the friction material on it contacts the gear, the resistance wedges the cone into the gear with more pressure, more resistance more pressure, less slippage, when the prop shaft/gear becomes the driving as opposed to driven then the wedge effect is reduced this causes slippage at the cone clutch due to the lack of pressure and in your case long engine running times will spin all the oil out of the the clutch area of the trans which may cause the noise you are hearing
Hope this helps
http://www.marinedieseldirect.com/ca...SHAFT&size=600

**Wotname** · 03-03-2016, 15:13

Quote:

Originally Posted by sartorst

......
Hope this helps
http://www.marinedieseldirect.com/ca...SHAFT&size=600

Yes, it does help

.

I must confess that until these last few days, marine cone clutch transmissions have not been an area of great understanding on my part. In the past, I have never had any transmission issues in the past and as the engine has less than 300 hours on it, I wasn't expecting any issues right now.

I'm hoping the problem is as suggested by yourself and others and not anything more serious but my cautious nature prevents me becoming too blasé until I get back to shore facilities - in a day or so!

I would of expected though the transmission could operate 24/7 without oil issues. I get the potential loading / unloading due to sea / wind conditions could cause cone clutch issues.

sesmith · 03-03-2016, 15:23

Is your PSS seal the newer vented version? If not, suspect air got trapped in the PSS bellows causing it to run dry and overheat. Temporary fix for this is burp the PSS seal. Permanent fix would be replace the PSS non-vented seal with the newer vented version.

**Wotname** · 03-03-2016, 15:35

Quote:

Originally Posted by sesmith

Is your PSS seal the newer vented version? If not, suspect air got trapped in the PSS bellows causing it to run dry and overheat. Temporary fix for this is burp the PSS seal. Permanent fix would be replace the PSS non-vented seal with the newer vented version.

Reasonable point however PSS is vented and I checked that water was present at the time.