Flywheel to Transmission Coupling Failure

SnrSlr

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Apr 28, 2014
7
Beneteau First 310 Port Orchard
I have a 1992 Beneteau F310 with a Volvo-Penta 2000 series two cylinder direct drive diesel and MS 2B transmission with a 2.37 reduction gear. In early July 2016 with approximately 1700 hours on the engine and transmission, the flywheel drive plate splines and transmission input shaft splines failed completely (stripped on their own, no collision) such that the engine would not turn the propeller. Fortunately, there was a nice breeze and we sailed back a couple miles to port.

Investigation of our failure found shaft to engine alignment very good (only 0.001 misalignment on a 3 inch coupling), no indication of bent shaft, and no indication of bearing wear or seal failure in the transmission. Examination of the damaged parts, however, identified that the shaft splines were only partly inserted into the flywheel drive plate. This may have contributed to the failure by overloading the reduced spline surfaces actually in contact.

As a minimum, we needed a new drive plate for the flywheel (a splined disc bolted to the center of the flywheel) and a gear set for the transmission. We were able to buy a drive plate from Volvo-Penta with an upgraded design that moved the drive plate splines toward the transmission (increasing engagement) and added some polymer dampening. After three months trying to get a source and delivery date via Volvo-Penta for the gear set, we went looking for a new transmission. We bought a new transmission (had to accept a 2.41 reduction) from French Creek Marina in Clayton, New York. The boat is reassembled and currently working fine but we have no way other than transmission removal to determine success of the design upgrade.

This past week we were made aware of a British Columbia, Canada company called Next Wave Marine Systems, Inc. with a solution called Suredrive marine coupling that replaces the flywheel drive plate and couples to the damaged transmission shaft without requiring a new gear set (see it at www.suredrivemarine.com). Had I known about this earlier, I would not have been forced to buy an entire transmission. Their design looks good but I don't know anything about their track record.

I lost the entire summer sailing season this year. Hopefully this information will help the next skipper experiencing this failure to a faster solution.
 
Apr 13, 2015
2
Beneteau First 29 Hamburg
Hi
If someone has a similar problem: Go for the Suredrive !

I had the same problem with my Beneteau First 29, VP 2002 engine and MS2B gearbox. I did not encounter a complete failure of the spline connection, but upon inspection i saw that there was not much missing. more than 50% of each splines on the gearbox drive shaft were gone, the counterside on the flywheel also looked bad, and there was a lot of "brown smear" around, which is probably from the wear off.

I then investigated my options, and also stumbled upon the Suredrive solution from Next wave marine.
The alternatives:
according to Volvo Penta: "Buy a new transmission, or, better, just buy a new engine" - much to expensive
Or milling a hexagonal shaft connection. One can read about this here and there, but i dont like this solution: Instead of 20 splines, there is only 6 faces at smaller radius for power transfer.

I decided for the Suredrive, and ordered it in Mai 2017, this year. Was a bit complicated to get it to Germany, and this caused few extra costs (tax, import, transport...). But it really is the perfect solution !
Meanwhile i have installed it, and had few engine hours already without any problems.
Installation is a bit of work, since you have to open the flywheel casing, and unmount the flywheel-screws. But its not really complicated.
In idle, the engine runs a bit smoother due to the damping element, but the most important: You dont have to worry about a spline failure ever again !


A convinced customer :)
 
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jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
This thread sounds like an advertisement for Suredrive.
 
Jun 2, 2007
403
Beneteau First 375 Slidell, LA
I agree. I experienced the same failure on my Volvo 2003, and a local repair shop was able to get a machinist to turn down the stripped splines on the transmission input shaft and fit a sleeve over the shaft with new splines cut into it, pinned in place. I did go to Volvo for the new design flywheel adapter plate. For this repair I didn't have to remove the bellhousing, which incidentally supports the motor mounts, so much easier. It's been 18 months now, so far so good.
 
Apr 13, 2015
2
Beneteau First 29 Hamburg
Sorry, if this sounds to much like an advertisement. I have no commercial connection to the company, i am just a very satisfied customer.
But half a year ago, i was searching the internet up and down for possible solutions to the spline problem. There must be thousands of engines of this type having this same problem, probably many people are simply not aware of it.
I could not find much of a help first, except this hexagonal milling approach in different variants.
I even tried to contact the company in GB (versatilemarine.co.uk, on their web page they describe the conversion), but never got an answer or even a quote. Maybe because i am from outside UK.
I also contacted a local machine workshop, but was not so lucky: they could not / did not want to help.
It was really frustrating !

If there is more good solutions to this probably very common problem, then even better:. Its the first time i read about the option you describe.
Lets collect some experience here. I am sure, there will be many interrested readers.


If you say, your workshop put a sleeve with new splines on the shaft: How exactly did they fix it there ? I guess, such a sleeve must be quite thin not to weaken the shaft.
I agree, removing the bell house cover is some additional work, and its not so nice, that you can not simply remove the transmission with the Suredrive installed. You have to open the bell housing again instead.
But in my experience, the main challenge was to get the flywheel bolts loose.This you have to do anyway to install a new drive plate.
Supporting the engine and removing the two engine mounts (6 screws) and bell house cover is not so much additional work in the end.
 
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Jun 2, 2007
403
Beneteau First 375 Slidell, LA
As I recall (it's been 18 months) the shaft was turned down to about twice the depth of the splines. The original diameter may have been 20mm or so, turned down to say 15mm. These are vague estimates. The sleeve was fixed in place by two roll pins (4mm diameter?) through the shaft at a 90 degree angle to each other. When I looked at it before installation, the assembly looked pretty robust.
When I experienced my failure and investigated on the internet, it appeared that this was a known problem, and many failures had occurred within the first 10 years of service, so I felt pretty good that my transmission lasted 30 years. I expect most of these transmissions that are still in service have already failed and been repaired. As it happened, the shop I brought my transmission to had a couple of old ones lying around, also with stripped input shaft splines. I pulled and replaced the transmission. The shop owner, after investigating parts prices (including a new gear set $$$), was the one who suggested going to the machinist he knew, who performed the shaft repair. He had to rent a special tool to cut the splines. The shop disassembled and reassembled the transmission, also replacing the seals while they were at it. I couldn't thank him enough. Casadaban Marine Works, Slidell, LA.