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Discussion Starter #1
Just did a transmission oil change on a yanmar 2gm20f. Have owned the boat for 2 years Pearson 303 1986.
Took out 540ml oil the required amount is 250ml for this transmission. I did check the oil level in the transmission several times and it was high on the dip stick. Should I put in the 250ml or put in what I pulled out?
 

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Put in enough so it's at the full mark. If your 2GM is like my 3 GM, the mark is a groove on the rod attached to the fill fitting.
 

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Discussion Starter #4
Thanks you do not screw it in to get the reading.
Just wondering if there may have been a reason to have put in so much.
I put in 300ml little above the mark.
 

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I wouldn't put even a ¼ teaspoon more oil than is recommended. Stick with the manufacturer's level and you should be fine. After all, some pretty smart folks designed your transmission to work with your engine and on a boat, so second-guessing them just does not make any sense to me.
 

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The excess oil may have been put in for storage. It's common to overfill to cover all the gears/plates and protect against corrosion, but it should not be run that way.
 

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Discussion Starter #8
Thanks, that makes sense as to how the oil got there. I was thinking it may have been done due to the angle of the trans. and I needed to put back in what I took out. So would you worry about the extra 50ml or just run it for a few hours change again, and put in the required 250ml? The plug vent is clear.
 

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Confusing question. Why not just fill it to the Full line on the dip stick.
 

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A few questions about oil.

What does over filling do? presumably harm... Underfilling seems like there would be inadequate lubrication.

Isn't there more volume in the engine (and the transmission for oil than the oil required?

Although I don't service my car... done by dealer service department... I don't recall any regular oil changes for the transmission. Tranny doesn't seem to consume oil...(the way engine does)... Why change it? Does it become contaminated? What is the grade of tranny oil determined by?
 

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What does over filling do?
Transmission oil does not typically cover the gears, rather it is splashed up on them and drains back down to constantly wash them. Overfilling causes the oil to aerate, rather than splash, which reduces its effectiveness.

Isn't there more volume in the engine (and the transmission for oil than the oil required?
Yes, and this is why many/most manufacturers suggest you top the transmission with oil, for winter storage. This covers the exposed parts of the gear.

Although I don't service my car... done by dealer service department... I don't recall any regular oil changes for the transmission. Tranny doesn't seem to consume oil...(the way engine does)... Why change it? Does it become contaminated? What is the grade of tranny oil determined by?
Not sure if your questions are about your car or boat. I'm only referring to boats, which have primitive transmissions, compared to automobiles. As the oil washes down the gears and plates, it removes wear. After a while, you can see fine metal in the oil, if you wipe the dipstick on a white cloth. There is typically no filter to remove this metal in our small gears. Most recommend changing at least annually.

Oil also has anti-corrosion additives that dissipate or decay, with simply the passage of time.
 
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If you see no signs of metal in the tranny oil would it be OK?

What grade of oil do marine transmission use? Same as engine?
 

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If you see no signs of metal in the tranny oil would it be OK?

What grade of oil do marine transmission use? Same as engine?
Wouldn't the answer be to simply follow the manufacturers instructions? The oil will eventually be contaminated and eventually lose it's additives.

Some gears take motor oil, others take transmission fluid.
 

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Minni... I am home at my desk and don't have access to the engine owners manual which is of course on board.... So I asked some questions.
 

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Although I don't service my car... done by dealer service department... I don't recall any regular oil changes for the transmission. Tranny doesn't seem to consume oil...(the way engine does)... Why change it? Does it become contaminated? What is the grade of tranny oil determined by?
Automotive automatic transmissions do have service intervals. They are usually 30-60k miles. Heat breaks down the friction modifiers and detergents.Transmission operation produces contaminates; metal and clutch material. 90% of automatic transmission fluid is 30 or 32 weight hydraulic oil with proprietary additives and red dye.
 
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