Kanzaki KB20 Gearbox/Transmission Problem

[James10016]

I need your help identifying the probable cause to a problem I am having with my Kanzaki KB20 gearbox.

The symptoms are:
1. The gearbox itself is stuck in Reverse.
2. The boat will motor in Reverse, with No unusual noise, such as grinding, screeching, scraping, clanking or clunking. Just like it did prior to this problem.
3. This is NOT a Shift Lever or Linkage problem. Because I have disconnected the cable link to the gearbox shift lever and can move it by hand.
4. Yes, I placed a 'witness mark' on the end of the lever cam shaft (that this lever is attached to) in order to verify that the lever was Not slipping on the shaft itself. This witness mark rotates the full 90 degrees back & forth, with the movement of the lever.
5. When moving the gearbox shift lever, there is 'No feeling that it is attached to the shift fork within the gearbox', because the lever will move smoothly through its entire 90 degree arc both ways, without any resistance.

I called the nearest authorized Kanzaki repair shop and the manager tells me that this is a new one to him. However, I'm not willing to remove the gearbox and turn it in for repair (which was estimated to be $500-$1500 unseen) without some idea of the real nature of the problem first.

Finally,...I need to tell you that, "No, I have not removed the shift lever access cover to look inside yet". I'd prefer to put this out on the internet first and see if anyone else has encountered this particular problem (i.e. look before you leap), before making any assumptions.

Any help or suggestions you might provide about this problem, 'IS' greatly appreciated.

Regards,

James

 

[Benny17441]

The KB series transmission has a forward clutch and a reverse clutch. The shift lever rotates the shift shaft which makes the shifter fork slide the shift ring into engagement with the forward or reverse gear clutch. The transmission itself is constant mesh with power transmitted to all gears and the selection of the clutches dictates how the output shaft rotates. Let me make clear that I have no first hand experience with the KB series but being the fact that the engine motors well in reverse with no clunkin sound I would say your problem lies with possible wear in the shift shaft, the shift fork or the forward clutch. I would start by removing and inspecting the shift fork assembly.

 

[KD3PC]

Critical to do this, before you get started ----accurately, make some marks on the cover defining it's position in relation to the reverser housing....before you take it apart. This will keep things in better alignment. I used a small chisel to mark both case and cover at the same time, same place. See manual below for why.

the shift cam moves the fork, which rides on a shaft with bearings in either side of the fork....could be a broken fork. All this moves a drive plate to and fro, it is spring loaded, so be careful when you take things apart, in case something actually broke. Parts may drop in your hand or in to the bottom of the reverser case.

I have attached a KBW20 manual (gold from a friend at Yanmar) from my old P42 that shows some of what you may have going on.

The rebuild price, if they are competent is a good one. Removal is a chore, and I would do it while hauled, just in case.

 

[James10016]

KD3PC & Benny17441,

Thanks for taking the time to reply to my message AND,...I especially appreciate, that KD3PC provided a Pdf file of my KBW20 Owner Manual. That alone saved me quite a bit of time and effort.

Yes, I noted that I needed to make a couple of alignment marks on the shift lever cover and gearbox casing in order to ensure it maintained the factory position/setting 'IF', I do take it apart.

However, I was hoping that someone in the sailing community may have encountered a problem like the one I have (with their gearbox) so, that I had an idea of what to look for when I went into mine. Plus, knowing the nature of the problem would help me determine the repair cost if it wasn't something that I could fix myself.

O.K. having said all that and looking at the shift assembly diagram provided on page 7-11 of this manual, it appears to me that the problem can only be one of three (3) things:
1) The Cam itself has been damaged or broken.
2) The Knock pin 'is stuck' in its tube and NOT engaging the slot in the Shift Fork. Thus, creating enough movement/play at the Cam end to enable it slip 'side to side' without moving the fork.
3) The shift fork itself is damaged.

I know these three (3) thing above seem highly unlikely. However, like I said before the Cam shaft will rotate, when you move the lever but, doesn't feel like it is moving anything within the gearbox itself and the Gearbox stays in Reverse.

What do you guys think?

Regards,

James

 

[KD3PC]

I'm still with the broken/damaged shift fork, only because it is the most likely part to have stress placed upon.

Second would be stuck drive plate or broken spring in the sliders

Given the cost of technology, I would beg/borrow/buy one of the cheap video cams that are on a flexible shaft and go through the fill hole and see what I can see.

Second I would suction out the fluids and filter them for pieces of metal. Then make sure you have the correct fluid and do it again.

If both of these fail to provide some guidance, then it is mark the cases/covers and pull the cover.

The lever movement is so easy/slight I am not sure you would "feel" the gears change. It is a really tight box and has support on the gear sets that make it smooth and strong.

You might call your local Yanmar shop, every now and then you can get hold of a guy/gal who has rebuilt these boxes and knows some better diags or shortcuts to test things.

 

[James10016]

ALL,

Hear's what I found out upon closer inspection of the gearbox.

I did Not need to pull the gearbox out of the boat after all.

It seems that the shift lever did in fact slip approximately 30-45 degrees on the cam shaft itself, putting the shifter out of alignment. Which explains why it wouldn't come out of Reverse.

Plus, I discovered that the shift cable has a 'kink' in it that caused the former boat owner to change the cable mounting geometry and hook up of the cable itself to the point that it created the need to place way too much force on the shift lever, which apparently contributed to the problem and lead to the lever spinning on the shaft in the first place.

Upon taking the shift lever off, you can see evidence of him trying to over tighten the clamp to keep it from slipping on the shaft. I might have to buy a new one somewhere, because this one cannot be tightened down anymore. The clamp is screwed down to the point that it is almost closed.

Bottomline: The gearbox is fine.

Moral of this Story: Always check the linkage and Connections first.

Thanks for ALL your help.

Regards,

James