Dropped a straw in my gearbox!!!!

[wsmurdoch]

Originally Posted by a64pilot

I think this transmission isn’t really a Yanmar? I know it says Yanmar on it, but I think it’s a Hurth? I say that as maybe the thread is different than what Yanmar uses in the engine that they build.

Yanmar KBW10, Hurth HBW10.... from the shop manual.

Bill

[Cool Hand Luke]

Originally Posted by kmacdonald

Sell the boat and let the new owner worry about it.

I will never buy a used boat ever again

[Swift Drift]

Ended up tapping the hole out to 1/8 NPT and using a brass plug. Will try and source a bronze plug later.
Everything is back together and performed well with testing at anchor.

Remember folks, never stick anything in a gearbox fill hole that’s shorter than the gearbox. Thanks for everyone’s input.

[Swift Drift]

Originally Posted by kmacdonald

Sell the boat and let the new owner worry about it.

There is a special place in hell reserved for people that do this.

[Wotname]

Originally Posted by Swift Drift

Ended up tapping the hole out to 1/8 NPT and using a brass plug. Will try and source a bronze plug later.
Everything is back together and performed well with testing at anchor.

Remember folks, never stick anything in a gearbox fill hole that’s shorter than the gearbox. Thanks for everyone’s input.

Attachment 214871

For future reference, you can fit a male NPT into a female BSP (in the these small sizes). It will be ever so slightly loose but works OK when a suitable thread sealant is used. However the reverse is not true i.e. a male BSP does not work in a female NPT.

If the large plug at the bottom of the picture is a anode (it looks like one to me), then the brass plug will be good for a long time; of course, a bronze one will be better!

[kmacdonald]

Originally Posted by Swift Drift

Well, during reassembly I snapped off the petcock drain at the bottom of the oil cooler. I was able to extract the remaining section and chase the threads in the cooler with a tap so they are good and clean.
Now I need to make a decision on what to plug the hole with. I’m tempted to use a stainless bolt with some tef-gel or lock-tite on it. But I’m concerned about the whole dissimilar metal scenario.
Am I making a bad decision by going with a stainless bolt? I think the cooler is bronze? Pretty sure the old corroded petcock was brass.

Attachment 214771

Attachment 214772

Ohhhhhhhhh boy. Here we go again!!!!!!!!

[kmacdonald]

Originally Posted by kmacdonald

Sell the boat and let the new owner worry about it.

Originally Posted by Cool Hand Luke

I will never buy a used boat ever again

Originally Posted by Swift Drift

There is a special place in hell reserved for people that do this.

For sale. Owned by a surveyor, rebuilt diesel. That means it had an oil change by a grease monkey.

[Boatwright]

Originally Posted by a64pilot

Usually they aren’t machine threads, often they are NPT.
If it’s machine threads then I’d use a bolt with tef-gel with the intent of changing it later with something bronze, if it’s NPT, then I believe I’d be tempted to use a PVC plug if you can find one, there is no real pressure there, and brass as a last resort, with the intent of later putting on what’s supposed to be there, surprised if it was brass.
I don’t have a cooler, but there are I believe similar drain pet docks on the heat exchanger and a couple of other places on the engine, one is I believe plastic.

Yanmar May also have used a wierd British thread, but I don’t believe this is really a Yanmar transmission, maybe not.
My 4-JHE uses this weird British thread on its oil galley plugs, I ran into that when installing an oil pressure gauge.

I think the KBW-20 is a Hurth transmission built under license?

Weird British thread is correct. Japanese and British pipe threads are the same. Since you are down on the Antilles, you may be able to find a Brit pipe-plug or pet-cock to fit. I wouldn't try to jam a mismatched bolt in and make things worse.

[Swift Drift]

Does anyone know where I can source a service manual for the KBW 21?
All of this messing about has inspired me to have one on board.

[jimbunyard]

https://www.manualslib.com/manual/13...age=159#manual

The 20 and 21 use the same manual. The link above is for the engine, the KBW20 and 21, and, I believe, but didn't look, the saildrive transmission.


By the way, not sure if, in the discussion about plug materials, anyone mentioned it, but it's better to have a less noble metal as a plug material than a more noble one, so that the plug 'sacrifices' rather than some other metal in the transmission. Probably best to have the materials within .15 V on the galvanic index, as described in this article, so neither 'sacrifices'.

https://www.corrosionpedia.com/an-in...rrosion/2/1403

[Swift Drift]

Originally Posted by jimbunyard

https://www.manualslib.com/manual/13...age=159#manual

The 20 and 21 use the same manual. The link above is for the engine, the KBW20 and 21, and, I believe, but didn't look, the saildrive transmission.


By the way, not sure if, in the discussion about plug materials, anyone mentioned it, but it's better to have a less noble metal as a plug material than a more noble one, so that the plug 'sacrifices' rather than some other metal in the transmission. Probably best to have the materials within .15 V on the galvanic index, as described in this article, so neither 'sacrifices'.

https://www.corrosionpedia.com/an-in...rrosion/2/1403

Thank you sir!

Thinking to to the future, does anyone know of a good source for rebuild parts? Clutch packs, etc.

[a64pilot]

Originally Posted by Wotname

For future reference, you can fit a male NPT into a female BSP (in the these small sizes). It will be ever so slightly loose but works OK when a suitable thread sealant is used. However the reverse is not true i.e. a male BSP does not work in a female NPT.

If the large plug at the bottom of the picture is a anode (it looks like one to me), then the brass plug will be good for a long time; of course, a bronze one will be better!

It will fit, sort of. I believe it will be ever so tight though, I know that you can tap a 1/8” BSP to a 1/8” NPT and if the BSP was larger, you couldn’t.
I gave up finding an adapter and based on advice from Mack Boring, tapped my engine to accept an NPT oil sending unit, Just put grease on the tap to trap any metal particles.

I would also say that if the plate is iron, then if you can’t find a bronze plug, and iron one ought to work. Iron plugs are common in house plumbing.
But the brass one will work, but I’d replace it eventually

[Gauti]

Just went through the same thing - used an endoscope. Extraction was via the cover plate/tranny cooler area on starboard side. I fed the endoscope through the drain hole and provided live coverage to a friend who was armed with a fine wire with a hook at the end. "Turn counterclockwise 90 degrees" and bingo.
I guess if it works in Antigua it works in Iceland. What a usefull thread this has been As for duration. This project kept three grown men busy for 3 hours, but then again it is out of there.