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4waves 15-09-2008 05:35

Excessive Wear on SD40 Yanmar Cone Clutch
Dear reader,

Are there any other users of the Yanmar SD50-4T saildrive that have similiar experience?

The product quality of the Yanmar SD50-4T saildrive, more precise its cone clutch, is an issue.

After less than 200 hours of usage the first cone clutch was so worn that it had to be replaced. Now the Yanmar 4JHI-TE (75 hp) has ran for 440 hours and it has the same issue, again the cone clutch has to be replaced.

The wear is causing the enigine not to drive the prop anymore, the cone just slips.

When sailing I allways put the motor in reverse to prevent unneeded wear.

This must be a design issue, Yanmar states 450 hours for a cone clutch assembly. That is incredible, not even 3.000 nautical miles with one cone set.

The cone clutch is stated to be a consumable and as such excluded from warranty! This can not be true, the part is just too expensive to have no warranty.

Has anyone had a similiar experience?



Chief Engineer 17-09-2008 15:43

What kind of oil are you using in the transmission?

S/V Antares 17-09-2008 16:11

Sounds like the Cable adjustment may be preventing the clutch from fully engaging, thus slipping the cone. Disconnect the cable and see if the leaver can be moved further in the same direction. Question? Is only Fwd or Reverse cone worn?

4waves 18-09-2008 00:07

Oil and cable of SD50
Dear reader,

In response to the two posts the following:

Up to now I have been using the Yanmar advised Quicksilver High Performance Gear Lube (a kind of 80W90 with dotations I believe).

I was advised to look at the alternative, ATF oil from Kroon.
The Quicksilver oil is very slow and might have trouble getting out of the cone fitting, the ATF might solve that.

The engine is driving a FLEX-O-FOLD 18"x13" prop.

In both cases the mounting and dismounting of the cone assembly was done by a professional technician from an authorised Yanmar dealer.

If I remember well I think that the first one did examine the lever. But as I understood the lever is supported by a spring that ensures the switch of cones.

The first time I had troubles they were both in forward and reverse, but mainly forward. The second time it is only forward.

I even think that in this second case there was allways some slip, because I could not get the boat to its old maximum speed anymore.



Chief Engineer 18-09-2008 17:42

Do not put ATF in the Saildrive.
Atf is not the same as gear oil.....they are used for two different things

4waves 19-09-2008 00:05

Dear Chief,

Could you elaborate on your statement.

ATF is even better quality than the 80W90 that is normally used. Why do you state so definite not to put ATF in a saildrive? Automatic Transmission Fluid seems to be able to leave the cone assy much quicker than the Yanmar advised oil. And other engineers state that the problem of the SD50 is caused by wear of the cones caused by slip, caused by the existance of an oil film. So putting in an oil that has the same or better lubrication but a different viscosity might be the solution to the issue.

On this forum I have found a lot of reference to ATF in saildrives, without the mention of any serious problems.



swagman 19-09-2008 03:24

Yes have had same issues (engine hours circa 1,000) a year back.
We did not replace due to horrendous costs quoted, but did redreill the engagement lever so we could further adjust the cable and effect more adjustment when in drive. Whilst now very clunky to engage (hope you know what I mean) we've not have any issues since. Certainly no repeat of that heart stopping moment when you need reverse in a pen and find its gone missing!

I was told that with this saildrive wear is aggrevated on the cones by users sliding the engine into gear toooo gently. Which indeed is what we always used to do. Not any longer.


GordMay 19-09-2008 05:58

The much lower viscosity of AFT (vs gear oil), can lead to premature wear.

4waves 22-09-2008 00:00

Dear Swagman,

Do you own a SD40 or an SD50? I made a typo when entering the thread subject line, I am an SD50 user.

I spoke to a technician last week about the cable/lever adjustment and he confirmed that the SD50 is using a spring supported lever to move the cones. Cable adjustment can nog cause/solve the isue he stated.

I do understand when you say cluncky, what I did not understand is "redreill", what did you change to make it work again?

The SD50 is a saildrive that is produced in Italy I have heared, can anyone confirm this. Other types are from Japan.



claire 28-01-2009 17:01

Yanmar SD40 design flaw
We have 2 Yanmar SD40 on our catamaran, installed in 2005. After the first one started slipping in the Panama canal (with less than 600 hours), we learned about this Yanmar design flaw that results in their SD40 saildrives slipping after just a few hundred hours. They know it and have a "warranty repair kit with new cone clutch assembly and new flywheel drive plate". They installed it on our 2 saildrives in Panama City. This is not a simple operation, the local mechanics had to re-do it 3 times before they got it right, and even now, one of the saildrives still makes an abnormal noise when in gear. The work can be done in the water.
We have been warned that this clutch remains a "maintenance item" !!!! that will probably need to be replaced every 600 to 1200 hours. It won't be done under warranty the next time. As a result, we are now saving engine hours whenever possible.

More info on this problem at: C:\Documents and Settings\ce\My Documents\bateau\equipment\engine\SD40 problems.mht

SeaKing 29-01-2009 21:20


Originally Posted by claire (Post 248845)

More info on this problem at: C:\Documents and Settings\ce\My Documents\bateau\equipment\engine\SD40 problems.mht

Claire that is a link to your C drive on your computer...kinda hard for everyone to read.;)

claire 29-01-2009 21:41

Oooops.... after some researche, here is the link:
Voyage Yacht Owners Association

swagman 30-01-2009 01:36

Hi Arne,
We've the 40 on a 75hp.
Be 'redrill' I meant putting a new hole in the saildrives gear arm, so we could force that arm to make a greater movement than was possible using the adjustment screws...........hope thats clear enough.
Looking back at logs - it began to slip circa 400 hours, was fixed maybe 550 hours, and we've since done a further 800 hours with no issues.
We too sail with the stopped engine in reverse, but as stated, since fixing it we changed how we engage gears.
Today we 'bang' the lever into gear as recommended by engineers, who told us the excessive wear was caused by our earlier gentler engagement.
Good luck

Captain Bill 30-01-2009 07:22

I have SD40s with approximately 1200 hours on them. So far I have had trouble with seals but no problems with the cone clutches. Now that I've said that they probably won't last the week. I have autostream feathering props and keep the tranmissions in neutral when sailing. I've been using quicksilver high performance gear lube. I find it interesting that the cone clutches can be changed in the water since they had to remove one of my sail drives to replace the front main seal. I suppose they could have removed the engine instead.

Meck 25-10-2009 11:08


Regarding the Yanmar SD40 Cone Clutch... We we coming down the fairway to dock yesterday and went to shift into reverse and the transmission made an ugly sound and we got no propulsion in reverse. The sound was kind of high rpm metallic slipping/grinding noise. Not good.

Then this morning while trying to diagnose the problem in our slip, we were able to shift from forward to reverse getting the prop to spin, but in forward at about 1500 rpm vibrations started to become noticeable.

Does this sound similar to the Cone Clutch symptoms.



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