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  Topic Review (Newest First)
12-15-2015 11:53 AM
KevinHerink
Re: Yanmar Transmission Clutch Problem

This is an old thread, but I thought I would post to it because I just rebuilt my Kansaki Hurth KBW10 transmission. The issue with the transmission was the forward gear was barely engaging, but the reverse gear seemed to work fine. The cost for a new transmissions today is about $4,200 which was a little steep for my old boat. So repairing it myself seemed to be worth a try. There obviously can be many issues with transmissions, but the KBW10 has a good reputation for being very durable. At the end of the day - I replaced 6 of the steel plates and 4 of the friction plates and got a whole new world of boat education. All of the the work I did was on the output shaft. The other two shafts were fine. If you are going to try this yourself, follow the manuals and keep the work place clean. I had two or three reference manuals and surprisingly some parts were referred to by different names - which was annoying.

Special tools needed -

Spanner nut wrench - Yanmar sells one, but it will be necessary to remove and tighten the output shaft nut
Gear Puller (local automotive store will loan you one)
1.5 foot piece of pipe that fits over the shaft, used to press the assembly back together.
Micrometer - measuring part for wear
Heat Gun


Pulling out the transmission - A chore in itself depending on your access to your engine compartment.
The transmission itself is small and weighs about 25 lbs. It's bolted up to the rear motor mounts, so when you tear it out you still have to support the back of the engine. But plan on your boat being down for at least a month. Everything takes time - Tear down, identifying parts, ordering parts, reassembly and installation.


Starting with the professionals -
First, I didn't open the transmission, I let the Yanmar repair shop in Costa Mesa open it. They told me the threaded end of output shaft was damaged and they didn't recommend repairing it. They disassembled the side plate and main housing and visually inspected the transmission. The shaft coupler, and the output shaft end nut were still attached and the nut appeared damaged (previous damage). Step one in the instruction manual is to remove the nut. I tried for about two hours to remove the nut, it was really not even recognizable as a nut it was so corroded and distorted. So I thought I would bring it to the professionals to remove the nut. They did not try to remove the nut, but removed the other covers. They charged $250 to open it up and inspect it, but they don't put it back together, so I brought down a five gallon bucket and collected the parts.

Damage on the threaded end of the output shaft -
I went down to a machine shop and they removed the nut from the end of the shaft. They had some special tools and actually cut the side of the nut and it popped off. They said they could fix the threads but they wanted the new nut for the end of the shaft. The shaft looked great except for the end threads. The new end nut was $50, but they traced the threads and the new nut fit perfectly Later, I discovered after torquing the shaft nut you stake it. Staking the nut means distorting the end threads so that the nut will not loosen. Some of the damage at the end of the shaft was actually when it was staked and then 35 years of marine environment.

Pulling the gears and components off of the Output Shaft -
Go to the local auto parts store and use their loaner program to access a free puller bring the assembled output shaft with you so that you know the puller will fit.

Best tip - Immediately before pulling the gears with the puller in place - take the heat gun and heat the gears and the parts to about 220 degrees farenhiet. It will be much easier to get the gears off if they are heated.

Place the parts in order in a clean spot in your work area and get out the micrometer and start measuring your steel plates and friction plates. Write down the measurements on a piece of paper for the forward gear and reversing gear for each of the steel plates and friction plates. Order new plates for any that are out of spec or close to being out of spec. You don't want to have to tear down the transmission again because the marginal parts have worn down in a couple of years.

Ran out of time - if you have questions you can send me an email - herinkk@gmail.com Bottom line - The replacement parts and the machine shop costs totaled about $850, but the transmission is still working great after a full year of service.
07-17-2013 03:59 PM
bristol299bob
Re: Yanmar Transmission Clutch Problem

Just saw this post so I am a little late to the party.

I've recently replaced the Kanzaki-Hurth KBW10 transmission on my yanmar 2QM20. I had similar symptoms as the OP. I decided to replace it with a with a good used unit, exact same model but newer. I have the failed original at home on my bench waiting for winter when I plan to tear into it.

I happen to have the factory manual for the KBW5/10/20. The OP mentions that he has the HBW10 and here is an online manual for that transmission: Boatinfo - Hurth 5 10 20 Service Manual

Briefly looking over that manual, it seems that the HBW is very similar to (if not the same as) the KBW. So that manual may be helpful to owners of the KBW as well.

I want to point out that I believe that the service bulletin referenced does not pertain to the KBW or HBW transmission. The service bulletin applies to:
"mechanical type gearboxes and sail drives only ... Marine gear Models KM2P, KM35P, KM35A and KM4A".
I believe these are the cone clutch style transmission that use motor oil in the transmisison. The KBW/HBW transmissions do not have a cone clutch and use ATF.

Which begs the question: where do the KWB/HWB faithful set the shift lever when sailing? I have always understood that for this style of transmission it was best to place it in reverse. A few mechanics have told me so, but I am starting to wonder.

I hate sailing with the trans "locked" in reverse because of the drag. I know I could squeeze another 2 or 3 knts out of her if I put it in neutral :-)
07-16-2013 05:11 PM
SlowButSteady
Re: Yanmar Transmission Clutch Problem

Quote:
Originally Posted by Rusty123 View Post
The referenced Yanmar tech bulletin says to leave the transmission in neutral during sailing, but that the shaft can be locked (with an add-on device) if the user doesn't like the prop rotation noise.

Question: what does prop rotation noise sound like? I get a faint squeal or whine (a little like a bad bearing) from my transmission when under sail in neutral. Is that sort of noise normal?
Often times a free-spinning prop will sound a bit like a low humming noise. There may be a bit of a squeal (if your listening to the transmission more directly, such as via an open lazarette), kind of like a car gearing down. If in doubt, take a look at the shaft to see if it's turning.
07-16-2013 02:51 PM
Rusty123
Re: Yanmar Transmission Clutch Problem

The referenced Yanmar tech bulletin says to leave the transmission in neutral during sailing, but that the shaft can be locked (with an add-on device) if the user doesn't like the prop rotation noise.

Question: what does prop rotation noise sound like? I get a faint squeal or whine (a little like a bad bearing) from my transmission when under sail in neutral. Is that sort of noise normal?
07-13-2013 01:28 PM
ncapener
Re: Yanmar Transmission Clutch Problem

I bought a pdf manual from the dealer. Covers transmission and 1,2 and 3 cylinder engines.
Send me your email and I send you a copy.
gonesailing4good@yahoo.com
Cheers,
Neal
07-12-2013 03:02 PM
Northsman
Re: Yanmar Transmission Clutch Problem

Quote:
Originally Posted by ncapener View Post
Hello,

I have a 3 HM 35 engine with a KBW10 transmission.
Recently the clutch started to slip, now it does not engage at all.
I took the transmission out and the cover off. I am looking inside the housing at two shafts with gears on them, a shift fork and what appears to be clutch plates on the larger shaft.
I would like to repair/ replace the gear box myself. How do I proceed ? Drawings or pictures available anywhere? I think, I can get the parts. I am not a mechanic, but I have a good set of tools and have taken a VW transmission apart once and changed the synchro rings....
Anybody done that job and can help?

If not possible to repair, Is there a way to lock the gear box in forward to get home???

Thanks,
Neal
I'm haveing the same problem as you With the transmission (gearbox) model KBW-10 mounted on an old 1979 model yanmar 20QM20 motor. Where did you get the gearbox manual and how did you solve your problem? In advance tks from Norway.
07-12-2013 03:01 PM
Northsman
Re: Yanmar Transmission Clutch Problem

Quote:
Originally Posted by ncapener View Post
Hello,

I have a 3 HM 35 engine with a KBW10 transmission.
Recently the clutch started to slip, now it does not engage at all.
I took the transmission out and the cover off. I am looking inside the housing at two shafts with gears on them, a shift fork and what appears to be clutch plates on the larger shaft.
I would like to repair/ replace the gear box myself. How do I proceed ? Drawings or pictures available anywhere? I think, I can get the parts. I am not a mechanic, but I have a good set of tools and have taken a VW transmission apart once and changed the synchro rings....
Anybody done that job and can help?

If not possible to repair, Is there a way to lock the gear box in forward to get home???

Thanks,
Neal
I'm haveing the same problem as you With the transmission (gearbox) model KBW-10 mounted on an old 1979 model yanmar 20QM20 motor. Where did you get the gearbox manual and how did you solve your problem? In advance tks from Norway.
12-22-2012 05:51 AM
Rockter
Re: Yanmar Transmission Clutch Problem

If you leave the transmission in reverse such that the gears cannot turn, how on earth does that wear the transmission??????

I cannot imagine anyone wanting the transmission to spin when you are sailing with motor stopped.

It is just needless wear.
12-21-2012 05:30 PM
Brent Swain
Re: Yanmar Transmission Clutch Problem

Mine will turn if left in forward but not if left in reverse. Left it in reverse for several Pacific crossings, no problems.
12-20-2012 11:40 PM
Goldfinger
Re: Yanmar Transmission Clutch Problem

Quote:
Originally Posted by ncapener View Post
I don't think that leaving the tranny in gear while sailing is a bad thing.
Yanmar advise against leaving it in gear.

edit: Sorry, didn't see the other posts until I posted this. Tried to delete but fail! Sorry to waste your time.
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