Correct Transmission fluid/oil for Kanzaki KH18 on Yanmar

Need help. My transmission was taken off and the seals replaced. IT has not been reinstalled. The Marine shop that did the work gave me 3 quarts of Automatic Transmission Fluid for the 1.7 volume of fluid it needs. The manual does not call for automatic transmission fluid. I have read a tread on the web that ATF killed his transmission on his Yanmar.

Does it need engine oil or automatic transmission oil, and what variety? I don't want to put the wrong oil after all that has been done to replace the seals.

Calling yanmar from there website leads to nowhere. Thanks for help.

Straight 30 weight motor oil. Recommended by Yanmar and Mack Boring. Been using it for years.

Jim

The information on this site had conflicting information, and after I rec'd the quarts of ATF from the marine company who is a Yanmar dealer when they serviced it, I needed to confirm my first impression of using engine oil not ATF. Engine oil is what I used in my 2GM20's transmission. Thank you Jim.

John
I'm fairly certain that years ago, it was Mack Boring that put out a written notice of a Yanmar directive to switch from ATF to 30# oil. Of course I never kept a copy of the notice, but I did switch to the oil and have not had a tranny issue to this point in time. Tomorrow is another day.

Jim

Hi gents,

I had this service manual in my Morgan files, which does say to use engine oil. In NE I tend to use Rotella 15-40 in diesel engines as it is heavy duty diesel oil covering a broad range of conditions and is relatively inexpensive. But for trannies, 30W probably is better up here, maybe 40W down south. My current trawler has an older Cat engine and it came with two manuals with different dates of printing. One calls for 30W in the tranny, the other calls for 40W so confusion reigns.

My newer Pearson yanmar 3HM used the red stuff, which I think when I changed it years ago was the then iteration of Dexron (not ATF) - the current Dexron VI being a magic elixir lubricant which I try to use whenever the option exists.

Best,

Peter

Pete
I always thought that the multi weight oils were meant for use in cold weather when a lighter viscosity would allow for easier starting. My thought was that since we almost never use the boats engine in below freezing conditions then using a straight weight would be a better solution. What do you think?

Jim

Hi Jim,

If you look at the grades vs temps on page 8 of the operations manual the viscosities vary by the temps we normally operate in up here in cape cod bay where the water temp at spring launch is just getting to maybe 40F and in the summer barely reaches 70. Air temps May to October can vary widely. Of course FL and other regions are a different story.

So I have had good luck with the Rotella 15-40 in a variety of diesel engines from small Universal, small Westerbeke, Yanmars, and 200HP GM, Volvos and Caterpillars. I have found it generally recommended by most in the know, including on web sites like Boatdiesel.com.

As to trannies calling for engine oil, it is a tossup between 30W and 40W, where I think you can't go wrong with 30W.

I have yet to consider going synthetic in marine engines, particularly where my engines tend to be on the older side of things before synthetics existed and so I dont want to do something the seals aren't used to. That said, my car requires synthetic 0-40W...

All that said, trusted mechanics who work on the specific type of engine are probably the best resource.

Peter

How about some "Alternate Facts" direct from the service manual

John, that is interesting. What model year is your boat? I wonder if the manual changed this from 1978. I will look again at mine as I may have missed read the manual.

John,
Coastie was Purchased new 9/1/78, hull #75 My fear of the unknown drives me obtain manufacturers workshop manuals for cars and boats. It is not an owners manual.
I have used ATF in the KH18 since date of purchase.

John (plural)
The notice that recommended the 30# oil in the transmission had come through Mack Boring as an after market directive from Yanmar. It was during the 1990s that I read it. I wish I had saved the notice. Until that time Dana's (hull #53, 1978) tranny had used ATF. Since then the 30# oil. Either one or the other or a combination of the both have kept unit in good shape. I do check the fluid a few times a year and change it every two to three year depending on engine hours. A suction device is used to remove the old fluid. The Yanmar manual mentions a drain but I never found one. When checking the fluid, I look for the clarity as well as the level. So far it has always been clean & clear.

Jim

Jim and John E, I heard nothing but crickets from Yanmar on my email to them on this question but I have also sent an email to Kanzaki Kokyukoki Mfg asking for clarification to which they actually responded, not with an answer, but with an acknowledgement that they received my question and that Mkt'g will get an answer to me in a few business days as to the correct lubricant to use. So we'll see. I'lI post any response I may receive. By the way, there is a drain plug on the very bottom that feels like a fastner but it is a small nut size bolt with a compression washer to seal the drain plug. However, when it time to change the oil/fluid, I will draw it out as the drain is essentially too low to capture in a container or to access well.

Maybe this happend to someone else? Around 1980 or so the KH18 started slipping. I contacted Yanmar and was sent a small packet of what appeared to be aluminum powder to add to the gearbox. a few years later the gearbox was making a fearfull noise so back to Yanmar. To my amazement they replaced the transmission no questions asked.

After all this time, this would likely not happen on our gears with all the age and use, but good to know that they stood behind their product then.

I decided to actually ck the transmission label for the model number and behold --- "ATF-A or 20/30W" as the "oil" for the transmission. So either one is can be used according to what is attached to the transmission itself. No wrong answer.