J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Transmission oil level

My transmission dipstick doesn't have any marks except for a groove about 3/16" from the bottom. The oil level is about half way up the dipstick. What is the correct level?

Not knowing if all 2GM transmission dip sticks are created equal with markings... I recommend you drain the transmission case, then refill it with .25 liter of SAE 10W-30 oil as specified in the Yanmar Manual. See where the oil level is on the dipstick once everything settles and that's where it is supposed to be!

Not exactly the answer I was looking for, especially since the oil is pristine and I suspect replaced by the previous owner last year. Where are the marks on your dipstick, measured roughly from the top?

My understanding was that the single mark near the bottom of the dipstick is the fill mark. When I drain the transmission and put about 1/4 L of oil in it, that's where it comes up to. (Actually, since I can't fully drain the transmission through the dipstick hole, 250 mL of oil is too much, I usually go for about 200 mL.)

If you clean the dipstick and find that the oil comes halfway up it, I think that means the transmission has been overfilled substantially. I have heard this is Really Bad. The yard does an engine inspection for me every spring, and they made a point one year of pumping out some oil because the transmission was slightly overfilled.

Transmission oil generally does look clear because it doesn't have to contend with the carbon from the engine. That doesn't mean it is clean and that it isn't causing undue wear on your transmission. As a matter of principle, I drain and refill the transmission oil at every haulout. I do it first, before changing the engine oil, so I don't contaminate the oil in the transmission.

My view on this: Oil is cheap. Transmissions are expensive.

Look at page 22 of a Yanmar Manual in this PDF document. It describes where the oil level should be for both the transmission and engine. The diagrams match what I have on Rhapsody.
http://www.guillermo.ca/pdf/yanmar.pdf