Excessive Wear on SD40 Yanmar Cone Clutch

[rgesner]

Nicely illustrated and detailed instructions or cone replacement or lapping:
Go to LeuCat's Merry Christmas And Happy New Year | LeuCat Adventures
and on the right side, under Favorites, choose
Get A Copy Of Our Yanmar Drive Cone Repair Manual

[Brickwede]

Hello,
I have now gained a lot of experience with the Saildrive SD40 and SD50.
If you have any questions, you can send me a PN.
But only after you have reading this repair report.
Repair report - Saildrive SD50 clutch upgrade kit - Hochseekatamaran Gerda Martha

[FPNC]

The SD50 drive has a cone clutch. Yanmar recommends the clutch cone be 'Inspected and replaced or lapped every 500 hours'. This is considered normal maintenance and does not require any further explanation by Yanmar. It is due to the cones not being able to hold the rated hp/torque for long term. The cones slip, they glaze, they wear.

These drives are way over rated for HP/torque. The 90 weight gear lube required in the transmission is also an indicator that they are pulling every trick to hold the gears together for that much rated HP / torque.

Boat builders demand larger and larger engines and do not want to give up the sail drive arrangement. The drive builders are fulfilling the request of the builders with no concern about field maintenance and reliability.

[skipperpete]

Hi Brickwede, good to see your posts about Yanmar saildrives, the information and your experience is a very useful asset to the forum members.

[Brickwede]

Originally Posted by FPNC

The SD50 drive has a cone clutch. Yanmar recommends the clutch cone be 'Inspected and replaced or lapped every 500 hours'. This is considered normal maintenance and does not require any further explanation by Yanmar. It is due to the cones not being able to hold the rated hp/torque for long term. The cones slip, they glaze, they wear.

These drives are way over rated for HP/torque. The 90 weight gear lube required in the transmission is also an indicator that they are pulling every trick to hold the gears together for that much rated HP / torque.

Boat builders demand larger and larger engines and do not want to give up the sail drive arrangement. The drive builders are fulfilling the request of the builders with no concern about field maintenance and reliability.

No, I don't think so. After 15 years of experience with an SD50, I think the Saildrive is sufficiently stable for engines up to 40 HP. I think it's problematic that Yanmar initially also equipped 50hp-75hp engines with it.
The whole clutch drama can be seen in small design defects. The copper discs are only available in 0.5mm increments. The adhesive force that allows the lower bearing to rotate in the circlips instead of on the copper washers and thus increases the clutch play very quickly.
But perhaps the defects are planned to enable service workshops to generate more and fast sales of clutch cones, shifters, Circlips and copper washer.

[motion30]

Consider this. Mercury marine has been selling outdrives with cone Clutchs for decades. Many with over 500hp. They are reliable and rarely fail. So yanmar could make a clutch that us reliable if they chose to. It is not a mystery

$$$

[FPNC]

I was there when Mercury started to offer the Bravo drives with diesels back in the 80's. The diesel engine torque and harmonics tore the clutches and the gears up. They then started using special hardened gears and created a 'Diesel Stern Drive'. A relatively small 6 cylinder diesel was tearing up drives built for big block v-8's. The diesel drives are only offered in very high ratios of 1.35:1 and 1.5:1. This keeps the torque damage potential to a minimum.

At that time, if we wanted to put an outdrive on a 3116, ~200 hp Caterpillar, the Kiekhaefer drive was the only thing that would hold up and it used a 71C Velvet Drive for the reversing clutch.

The same thing happened when a higher HP Yanmar engine was connected the Volvo Duoprop drive. Those drives held up pretty good with a relatively tame Volvo diesel but would not last 2 seasons with a higher torque Yanmar turning them.

Diesel torque and harmonics are a contentious problem in drive systems.

[motion30]

[QUOTE=FPNC;3863441]I was there when Mercury started to offer the Bravo drives with diesels back in the 80's. The diesel engine torque and harmonics tore the clutches and the gears up. They then started using special hardened gears and created a 'Diesel Stern Drive'. A relatively small 6 cylinder diesel was tearing up drives built for big block v-8's. The diesel drives are only offered in very high ratios of 1.35:1 and 1.5:1. This keeps the torque damage potential to a minimum.

At that time, if we wanted to put an outdrive on a 3116, ~200 hp Caterpillar, the Kiekhaefer drive was the only thing that would hold up and it used a 71C Velvet Drive for the reversing clutch.

The same thing happened when a higher HP Yanmar engine was connected the Volvo Duoprop drive. Those drives held up pretty good with a relatively tame Volvo diesel but would not last 2 seasons with a higher torque Yanmar turning them.

Diesel torque and harmonics are a contentious problem in drive systems.[/QUOT
I can agree with you that the torque at the low RPM is a drive killer. I don't know what the torque rating for these small days will are but the Mercury's from 525 has a peak torque rating of 540 pounds. In the clutch drive survive in that application. The point I guess I was making to have the service these things in such short intervals as ridiculous and a failed product as far as I'm concerned. Reminds me of the Yamaha 350 horsepower outboard that had to have the flywheel replaced every 50 hours


Particular in the marine environment when these systems fail we just can't pull over on the side of the road and call tow truck. sometimes a member would be thousands of miles from sure and help. They should do a better job