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Yanmar / Kanzaki gearbox dipstick threads broke

kbgunn

.
Sep 19, 2017
145
2006 Hunter 38 4410 Lake Lewisville, TX
Documenting for future inquirers. I have a Yanmar 3JH4E with the Kanzaki KM35P gearbox (transmission if you prefer). The oil dipstick broke off at the threads with the threads left behind in the gearbox! Apparently this is a common occurrence because the parts guy said they send them out regularly. I puzzled over how to back the threads out when the replacement arrived. I found the start key had an ear shaped just right to wedge in the remaining threads and back them out. Be careful not to drop plastic bits into the gearbox. The replacement is part # YAN-177070-02450. The engine and gearbox codes up above will help you find a parts manual by web search.
Pics below.
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Likes: JoeWhite

Nodak7

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Sep 28, 2008
1,186
Hunter 41DS Punta Gorda, FL
Yup! Pretty common problem with that transmission! I replaced mine and carry a spare.
 
Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
Just out of curiosity, how much did the new yanmar dipstick cost including shipping?
I replaced mine, two years ago, with a custom stick from www.CariblueMarine.com
You can save the stainless steel dip stick tube from your existing cap to use in the new cariblue cap to save $5. Total cost including shipping is $80.
I know, it's a lot of money for a dipstick; however, the quality is superb. All aluminum with aluminum threads, will never have another plastic dipstick break again. Check it out, I think you will be impressed.
 

Nodak7

.
Sep 28, 2008
1,186
Hunter 41DS Punta Gorda, FL
I bought it at our local Yanmar parts store and if I recall correctly it was around $30. I thought that was pretty high.
 
Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
I bought it at our local Yanmar parts store and if I recall correctly it was around $30. I thought that was pretty high.
I am not surprised of the cost if that included the cap and ss tube. If it only included the plastic cap, I agree that it is a rip off; however, Yanmar parts are notoriously expensive!
 

Nodak7

.
Sep 28, 2008
1,186
Hunter 41DS Punta Gorda, FL
I am not surprised of the cost if that included the cap and ss tube. If it only included the plastic cap, I agree that it is a rip off; however, Yanmar parts are notoriously expensive!
It was the complete cap. Plastic and metal.
 
Jan 7, 2011
2,817
Oday 322 East Chicago, IN
Is the new dipstick any better than the old one? I would proactively replace mine, but if it is identical (same propensity to break off), not sue it is worth it…unless the failure is “time-related”…in other words, more prone to fail due to age.

On my BMW roadster, the fan blades are prone to fail and tear up a nice hood after time. Some guys pull the fan completely (fan-delete they call it)… I thought it good insurance you just replace the fan proactively on my 21-year old car.

So is changing the dipstick cheap insurance, or just a waste of money?
Inquiring minds want you know…


Greg
 

Nodak7

.
Sep 28, 2008
1,186
Hunter 41DS Punta Gorda, FL
Is the new dipstick any better than the old one? I would proactively replace mine, but if it is identical (same propensity to break off), not sue it is worth it…unless the failure is “time-related”…in other words, more prone to fail due to age.

On my BMW roadster, the fan blades are prone to fail and tear up a nice hood after time. Some guys pull the fan completely (fan-delete they call it)… I thought it good insurance you just replace the fan proactively on my 21-year old car.

So is changing the dipstick cheap insurance, or just a waste of money?
Inquiring minds want you know…


Greg
Exact same thing! You just have to be extra careful when you tighten it down!
 

kbgunn

.
Sep 19, 2017
145
2006 Hunter 38 4410 Lake Lewisville, TX
I paid $37 plus $10 shipping for the Yanmar part. It appears to be the exact same material as the original. The boat is a 2006, so the original lasted 15 years. I expect the same life span out of the replacement. I'm sure the milage will vary and depending on duty cycle.
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
I have to wonder why the plastic screw cap broke. Any chance it was due to overtightening over the years ? Just tighten until snug as the O-ring ensures no leakage.

I replaced mine, two years ago, with a custom stick from www.CariblueMarine.com
I've seen these custom sticks mentioned in a previous post some time ago. Did you ever wonder WHY the transmission manufacturer decided to use a plastic threaded cap rather than a metal one ? This didn't just come to the mfg. in a dream. If you cross thread the threads in the transmission casing you are royally screwed. Or unscrewed, as the case may be :facepalm:. Shaft removal, shaft coupling removal, transmission coupling removal, casing removal. The transmission coupling removal looks the most interesting of all. And then reverse the operation.

The plastic cap ensures you NEVER damage the casing threads either by simple wear or most likely, cross threading. And speaking of stripping the threads "


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................... the threads on the new dip stick are "hard anodized aluminum." Shouldn't be any worry about possibly damaging the casing threads there :yikes:.

The annual oil change in my transmission is always a roaring hairy event as there is only a few inches clearance above the filler hole in which to pull the dipstick. Replacing the filler cap is done blind and is a cross thread waiting to happen.

Do yourself a favour and don't over-tighten the filler cap. Or as someone has repeatedly said here "Your boat, your choice." No names.

BTW @kbgunn , excellent photo layout of the failed cap and removal.
 

Nodak7

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Sep 28, 2008
1,186
Hunter 41DS Punta Gorda, FL
Ralph you have pointed out an excellent reason to stick with the original equipment! Thanks!
 
Apr 8, 2011
461
Hunter 36 Deale, MD
+1 on the Cariblue Marine dipstick. I don't ever have to worry about plastic pieces ending up in my transmission again, and I don't have any trouble not cross-threading the much better made dipstick even if I have to contort myself a little to get to it. I'm not in a hurry and the Cariblue dipstick mates with the threads like a nice piece of German engineering - its very well made. And I don't over-tighten it.

I call BS on the crumbling plastic OEM dipstick. I've never seen any other dipstick in any other vehicle do that - car, boat or airplane. I'm not gonna have something like that in a VITAL bit of my boat's machinery that I know WILL eventually fail with no warning, and possibly damage or ruin my transmission. I respectfully disagree with the equivocation that the plastic the OEM dipstick is made of is a better material for this application to prevent stripping or cross-threading. The risk of transmission damage is not worth it to me. These failures are very common and pop up frequently here and on other sailing boards, and I've yet to see anyone post anything negative about actually using a Cariblue anodized dipstick after they've bought it as a replacement. I've been using mine for three seasons now and its one piece of equipment that I'm increasingly confident is off the "keep an eye on" list.
 
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Likes: BigEasy
Oct 29, 2016
1,765
Hunter 41 DS Port Huron
@Ralph Johnstone like you said your boat your choice, but I look at how many covers, caps and plugs on engines and transmissions that are aluminum or steel and have yet to fail. As for cross threading I think I would have to intentionally try to do that and even then it would be tough to accomplish so I am not worried in the least about your concerns. Having to jam a foreign object in the broken thread shank would have me more concerned then cross threading while threading by hand.
 
Last edited:
Jan 7, 2011
2,817
Oday 322 East Chicago, IN
My 2GM20F is about 33 years old, and still has the original dipstick (I assume). I guess I am just careful not to crank it down too tight.

Greg
 
Jun 21, 2004
1,849
Beneteau 343 Slidell, LA
Heat, Oil, & plastic threads are not a good combination. Very common to hear about the plastic dip stick breaking off. Personally, I don't think that Yanmar intentionally selected a plastic head & dipstick for the transmission to prevent cross threading; I think they simply choose to install a less expensive alternative. I am not concerned about cross threading the cariblue dipstick, the threads engage nice & smoothly into the transmission, unlike the cheap plastic diptstick that is prone to cross threading. Would you use a plastic plug in the oil pan on your engine???
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
Would you use a plastic plug in the oil pan on your engine???
NOPE ! Because if it failed in operation ..................... you can guess the rest.

If it were the plug for the filler opening, no problem.
 
Mar 6, 2008
680
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
For those who like to use plastic, would it help if some lanolin is applied to the thread before inserting?