Oil Levels

Ahoy All , I really like my F/G engine pan to be oil free and of course diesel fuel free as well .

I have just installed new fuel lines with those new copper washers , in an effort to stop the diesel fuel from dripping into my f/g engine pan.

I purchased new fuel lines , those with the banjo ends , and installed them in hope to stop diesel fuel from dripping from those connections !

Oh , Gosh , I still have a diesel fuel leak from one of those “banjo” fittings , What to do Next ???

B T W , upon re-reading the Yanmar Service Manual for a 3 GM engine , page 11 - 7 it says to : " check the clutch case oil level without screwing in the cap . "

On the transmission , my oil level dip stick , has only one circular or anular ring on that dip stick !

There is NO upper limit , or is that annular groove , the upper limit ???

Soooo just where is the lower limit ring ?

Has anyone else determined what is the specific measure for the oil level in the transmission for a 3GM30 engine ?


Calliste’s 3GM30F is likely mated to a Kanzaki Kokyokoki KM2P reduction gear (which is what Zygote has). The oil capacity of the gearbox is 300 millilitres.

300 mls = 300 cc and (if I remember the conversions correctly 300 mls is about 0.6 US pint or 10 US fluid oz or 10.5 UK fluid oz or 0.5 UK pint; just remember that a pint ain’t a pound the world around and stick to metric).

Yes, the oil dip stick reads correctly when the cap is resting on the lip of screw-thread of the gearbox casing.

If you add 300 millilitres to the gearbox casing, the oil level should be at the upper mark on the dipstick. I think there is a second, lower, mark on Zygote’s gearbox dipstick for the minimum oil level, but I’d have to go look to make sure.



Hi Bil , Thank You for your reply .

Sounds like I may have to drain the tranny oil , refill it with only 300 ml , then

check the oil level on the dip stick, to see how close it comes to the annular

groove near the end of the dipstick.

BTW , what is your oil of choice for the engine crankcase and transmission ?

After re-checking “Another Cruiser’s Bookshelf” the two oil articles found there,

I was not sure that the synthetic oil is Ok to use with older diesel Yanmars , and

certainly no mention of using synthetic engine oil in the transmission .

Douglas: Hi!

As you know, we usually have Zygote loaded with her design LWL an inch or so below the actual WL. For simplicity of stowage on a voyage, my ideal is to stow just one type of oil and to use the same oil in the Yanmar 3GM30F crankcase as in the reduction gearbox. In reality, I usually have three oil jugs in the lazarette: an empty jug for holding used oil (before proper disposal ashore) and one jug of fully synthetic and one jug of traditional (aka dino) oil.

I have tried dino oil, semi-synthetic, and fully synthetic oil in Zygote’s 3GM30F crankcase and the transmission.

I found back in about 2003 that the engine burnt oil at a noticeable level when using a fully synthetic oil. I like upper-cylinder lubrication, but not that much.

For the past 7 or 8 years, I’ve been using a semi-synthetic oil in the engine crankcase, to get some of the benefits of synthetic oil but controlling the burning. I make my own semi-synthetic oil, just by adding a small proportion of a fully synthetic oil (about 1/3) to dino oil. I’ve been using full synthetic oil in the reduction gearbox.

I’ve not had any problems with oil seals due to my use of synthetic or semi-synthetic oil. I’ve not done any oil analysis, so I don’t have any evidence to talk about oils and wear. But the industry experts all assure us that synthetics are best for preventing wear and because they oxidise and deteriorate less with time. And that semi-synthetic oils deliver some of the benefits of synthetics.

I’ve not got around to unscrewing the gearbox dipstick yet and checking. Sorry! I think that the annulus about a fingernail’s breadth above the bottom of the dipstick is the maximum mark. I’ve always used an extractor to suck the gearbox as dry as possible and then I’ve then added a measured 300 ml oil to the gearbox (and I think the oil level has met or got close enough to the annulus).

I have no evidence to contradict my father’s wisdom: that engines in small sailboats are more likely to die of disuse and neglect before they die of wear and tear.



Thank You Bil , for sharing your choice of engine oil and gearbox oil.

I can agree with what your dad said, as well , once I learned that a sailboat

spends about 90% of it’s floating life, in port.

Everything I have read says it is fine to mix synthetic with what you call “Dino” oil.

BTW , (since this is an engine and propeller catagory) I was not as sucessful as

you with preventing bio and scale growth on the prop, using Beechams waterproof

grease and woman’s nylon ankle socks over, on the prop blades .

After this next prop cleaning , I am going to try the black plastic garbage bag ,

enclosing the prop totally . I have great trepitation about this as it may reduce

the water oxygen levels so much as to create worm hole corrosion on my SS prop shaft.

When I replaced the prop shaft in S F circa 1996 , I installed an Aquamet 22 ss

shaft and to this day there has been no visual evidence of any corrosion, what-so-

ever, Phew !

Ahoy Bil , you saved me , yet again ! I Finally got time to change the oil in my 3GM30F Yanmar engine marine gear , AKA the transmission .

I found a drain plug, under and aft of the xmission shift lever, and drained the oil.

Later , I replaced the drain plug and added as you suggested 300 ml of oil .

Previously , I had over filled the “gear” as per following the table in the thick Yanmar Service Manual , page 11 - 7 under 1.2.9 oil capacity , clutch case coluum, which stated for the 3GM = .7L which = 700 ml .

After a mostly motor voyage to Palau Tioman , I noticed some oil leaking from that marine gear .

Upon refilling the gear box with 300 ml , I noticed that the oil didn’t reach even the bottom of the dip stick, but by adding another .65 ml , the oil was right at the annular groove on the dip stick.

Further curiosity lead me to read the data plate on the engine bell housing, which I hadn’t noticed before.

That data plate stated an oil capacity of 0.35 Ltr , and also stated that the gear was a Kanzaki , model KM3P .

I choose as you did to use fresh Synthetic oil in the gear !

For our other BCC owners with 3GM30 Yanmar diesels , I caution you to be v careful about what you read in the Yanmar Service Manual that comes with your engine , as I have found even more descrepencies .

BTW , I sure do miss Marty Chin’s advice to our forum as well .