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AdamY 18-11-2006 08:34

Tranny burning up (longish)
Okay so we departed San Diego Wednesday moning hoping to make the 6 day passage to Bahia Magdelena and for the first time on our trip had a nice fair sailing breeze (probably our first mistake )

We sailed off the wind and into the night with a double reefed main prevented and ran at around 4 knots most of the night. a couple hours shy of the dawn our wind dropped and our speed with it. When dawn came I woke Kristina and shook both of the reefs out of the main but found our speed still well below 3 knots. we were eager to get to Mag bay because a friend of ours was flying in to Cabo on the 17th to take a bus up to Mag bay and join us for 3 weeks.

I fired up the engine and put her in gear to find that we couldnt make more than 2 knots under power. I checked the transmission and found that it had gotten very hot and the oil inside of it was burnt. The shaft was turning slowly but I could now get the engine rpms up to 3400. previously under load I couold never exceed 2800. I concluded that the transmission was probably slipping. we had it rebuilt before we left portland just a few months ago but it seems to be suffering a serious failure. I put on my snorkel and dove on the prop. we had wrapped it twice on kelp in Catalina island and san diego respectively but I knew the engine RPMS would have lowered, if anything, from the prop being wrapped, still I jumped in the cold water and found a nice clean prop. I had a decision to make. we were now 30 miles south of Ensenada which is the largest city on the west coast of the baja peninsula and the last place for 800 miles or so witih a boat yard where we could possibly find a mechanic and/or parts to do it ourselves. being 20 miles offshore meant we could close/beam reach the whole way back which would be faster than the run we were making.

Fortunately the wind picked up in the afternoon and I was able to push her hard heeled over around 6.5 knots for most of the afternoon. Once we approached Bahia Todos Santos (about 10miles out from Ensenada) the sun began to set and with it the wind began to die. we were miraculously able to make 3 knots in around 6 but I decided we needed to get there and hoisted our biggest "go faster" spinnaker. At this time we were doing less than 2 knots and when I got the sock up the spinnaker just sollapsed.

if my 1000 sq ft 3/4 oz spinnaker wont fill there really is ZERO wind.

Anyway I fired up the engine despite the heat of the transmission and we limped along at a speed that fluctuated with the swell from .5 to 1.5 knots. it took us 8 hours to motor the last 9 miles into Ensenada and we are currently tied to an expensive marina.

Okay i've bored you with a long story just to ask my question.

Anyone think my transmission isnt totally hosed? I had the transmission rebuilt 4 months ago prior to setting off on our cruise and am loathe to jack up our recently remounted realigned engine and pull our recently rebuilt transmission to have it rebuilt all over again (if it isnt totally destroyed that is).

Anyway, I would love to hear some expert opinions. I am going to go see a mechanic tomorrow about it, on the bright side they are much cheaper here than in the states, but I really dont want to have to lift the engine and realign it.

Anyway, sorry for the long post.

Thanks in advance.

never monday 18-11-2006 08:45

First, need to know what trans/engine combo you have.
Second. You should be able to pull the trans without disturbing the alignmaent. It takes alittle more time and precaution. In the endi it's easier.

AdamY 18-11-2006 09:06

Duh, good point.

I have a Yanmar 2M20 with a Hurth KBW10 Transmission. I'll edit thepost to include this.

FWIW the hurth dealer in Seattle didnt have KBW10 clutch kits but said the ZFkitwas identical and should work just fine. The Hurth service person who rebuilt it concurrered and used the ZF kit.

On the bright side the old clutch kit was still servicable and I still have it so if I have to do that I wont have to wait for parts.

I am very much in doubt that I can get the tranny out of my engine compartment without jacking up the engine but if it can be done I will do it that way, I really dont want to jack up the engine again.


never monday 18-11-2006 09:22

Ok, this will be long and rambeling. I don't write well but rater write how it comes out of my brain.

I'm assumeing you have a 2QM20. The KBW10 is a PIA trans. It will require special tools to take apart. Getting it off will be easier. Loosen the top mounting nuts. DO NOT touch the lower ones. Put you jack under the engine, drop the shaft off abd push it out of the way. next remove the shift cable and mounting ears from the trans. When you pull the ears the top nuts will need to be removed first. DO NOT mess with the bottom nuts on the mounts. Unbolt the bell housing bolts and slide the trans off.

You might be able to save it by just flushing and refilling with new oil, but I doubt it. I have no info on the ZF parts Vs Yanmar parts. I try not to mess with that trans and just replace it, about $2200

Alan Wheeler 18-11-2006 12:37

As Pat stated, it needs special Factory tools to work on this thing and especially for set up and assembly of the clutches and thrust washers. They have to be just right or.......
So you need someone that has the experiance and the tools to work on it, or you are wasting your time.
Things for you to check though.
Is the Oil level OK?
Is there any water contamination in the oil?
Was the correct oil used in the first place? That one is criticle.
Does this have an oil cooler? if yes, check it is clean and you have good oil flow and that the oil is indeed being cooled. In other words check that the water is flowing through the cooler. This is where water can get into the trany by the way.
Check that the fwd/revs lever is moving all the way.

Now a couple of points you can't do anything about, but.. when it was rebuilt, did they do anything with the pump?? It could be that the pump is not producing enough pressure, due to being worn.
There may (or may not) be a pre-filter on the pump intake. Is that clean. Unfortunatly it's not a thing you can easily get to and if it is blocked, then you have other issues anyway.

And finaly, was there any warranty with the last repair. Because I would be throwing it back at them. And I am assuming they know what they are doing??

AdamY 18-11-2006 12:53

The guy I had rebuild it was the guy the Yanmar dealer in Portland reccomended so technically it was the Yanmar dealer's guy.

The transmission was fine before the rebuild and there has been burning oil ever since the rebuild.

but I didnt really notice it till we left. also since the rebuild oil has leaked out the rear seal but since the engine was realigned before we left causing it to be much further aft and tilted significantly more than it was previously we dismissed the issue as being related to the angle of the transmission.

Anyway, I am going to call the guy first thing but we are moving to the Baja Naval marina first, they are cheaper and have an impressive facility that I believe is capable of dealing with this issue if I cant get it solved by the original guy or myself.

Any idea if there is anything that can even be adjusted with the transmission in place. it is a pretty simple machine that seems to have very little in the way of exposed bits. The first thing I did offshore when this happened was make sure it wasnt the linkage which is why we had no reverse coming into the marina. I detached the cable and shifted it into fwd manually but reattaching the cable to a searing hot shift lever proved difficult.

Please keep the conjecture coming it all helps.

Sadly I think this machine is pretty simple and going to need to come out, but we'll see, im going to flush the oil out of the tranny and put fresh stuff in before I try and sail her from the one marina to the other in hopes it might at least improve performance.

Thanks again,

Starbuck 18-11-2006 13:16

It's the non-spec clutch kit that makes me suspicious. If you have the old one, could you try swapping it out and seeing what happens before you tear deeper into the case?

Alan Wheeler 18-11-2006 18:06

Oil should not leak from any seal no matter what angle the box is on. That is a tell tale sign something is not right in it's self.
Sadly I think the damage has been done. If the box has gotten that hot, it will be because a clutch is slipping and slipping badly. This will burn the oil and contaminate it with friction material from the plate. Clean oil may get you somewhere, but I suspect it will not be for long if it did, so don't rely on it.
For every 10degrees C you have in Oil temp rise above normal, you effectively halve the life expectancy of the trany. That is a rule of thumb, but is a fairly close rule.

Alan Wheeler 18-11-2006 18:08

Oh another thought, does your box have an oil pressure gauge at the helm console?? Is it reading lower than normal??

never monday 18-11-2006 22:08

It's a basic box akin to the Hurth HBW100

Alan Wheeler 18-11-2006 22:40

arrrr, Splash type?.
OK, ensure two things. Ensure you have the correct oil. ATF!!!!! Not criticle enough to have caused you problem, but still important.
Ensure you fill to the dipstick full mark ONLY!!!!!! DO NOT OVER FILL!!!!!!! This is most important!! Over filling will cause the issues you have described. It can cause seriouse over heating and it can cause the seal to be blown out.

AdamY 19-11-2006 09:00

All this great advice, I am in your debt, thanks to you both.

In answer to your questions. I dont think there are any fancy pumps or coolers in this box.

The tranny came with the same oil in it the engine takes and the dealer in Seattle as well as the buy who rebuilt it said that with the KBW10 I can use either SAE30 or ATF. Since having one type of oil on the boat was appealing I stuck with the engine oil option.

I was told by my rebuilder that there is a vent hole in the dipstick that will allow any excess oil to leave the case without causing any damage (guess that is another one to talk to him about) but that as long as there was some oil I would be fine. He also said that with the new angle the fill mark would be dubius as there would be less oil touching the stick than there was when it was flatter and that if there was any on it it was probably full.

I am starting to doubt my rebuilder guy ;-)

I am going to try and pull it today after I find out if I can rent tools like a jack etc. from the yard here.

Oncce I have it pulled I will try and dissasemble it using my excelllent Yanmar service manual as a guide and I will try to put my old clutch plates in.

I know I should have a professional do it or replace it but we're on a budget and what is the point of having something on the boat I cant fix.

Out of curiosity, if I bought a new ZF12 from the dealer in Seattle, would you still tell me to have that one repaired professionally or is it the KBW-10 that is specifically such a pain that you think I wont be able to figure it out?

Thanks again for all of your help.

never monday 19-11-2006 10:29

Heres a "trick of the trade" for you.

Skip the jack. Go finsd a ball, preferably a soccer or basketball. Deflate it and slide it under the oil pan. Now start inflating it. have just built an air pressure lifting machine.

I'm going with the ZF would be a PIA also. I realy don't like the clutch pack set up.

DeepFrz 19-11-2006 11:40

Adam, you keep mentioning the change of angle. I thought the angle of the transmission would be determined by the angle of your driveshaft and stern tube. Why is your transmission at a different angle than it was previously?

If your transmission is at such an angle that the oil would only show at the very bottom of the dipstick is the angle exceeding the specifications? And is the angle of your engine within the engine specs? Does your system use a Z drive?

Some thoughts and questions from a "non-expert".


Alan Wheeler 19-11-2006 11:50

OK, firstly to make things entirely clear. Pat is the pro. He has the years of experiance. I don't. I simply teach this stuff as a job and I have "bits" of knowledge gained study for what I teach, from broad experiance and/or talking to experts.
What I suggest, and maybe Pat can help here, is that you need to know exactly what the max angle this box can be installed at and if yours is within that spec.
It is NOT recomended that you run the box on 30weight oil. However, it also will not do any short term damage and 30W will get you out of a bind. BUT! ATF is far thinner and is better suited to keeping oil bathed friction plates lubricated and cool. Remember, the two oils are very different and designed to do two compleatly different jobs.
The "hole" is a breather only. Not for Maintaining an oil level. That is what your job is.
This is what I suspect has taken place.
The box was either over filled, or the angle of the box means the criticle area of the box is over filled and the box has severly over heated. This has caused the 30W oil to allow the friction plates to slip. Once that has happend, the box has gotten hotter and the oil is breaking down and the plates are slipping. the excess oil pressure and oil weight is creating excess pressure on the rear seal and pushing it out.
What I suggest!
Go with Pats original thought of changing out the oil. Give the box a good flush and place the correct ATF oil in it. It just maybe that the 30W oil is simply lubricating those plates to much now that they have "shined up".
I also suggest you contact Yanmar and explain what has happend and ask for there advice. Especially on the angle of the box install.
Make sure that rear seal is tapped back into place if it has pushed out. The correct oil and level should stop any leaks.

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