Where do I put oil in for the gear shift?

I have a 1978 Mercruiser 120 hp... there is a box on the transmission behind the motor on the left hand side. On the side of the box it says to use 10w30 oil but I see no place to put the oil in. I want to know where to put the oil in and the proper way to fill it.Where do I put oil in for the gear shift?
You are probably just seeing a label for the motorindicating to use 10w30 oil in it. There is not really a transmission behind the motor before the transom. What you are referring to as the transmission is only a housing. It covers up the flexplate, engine coupler, and driveshaft. The transmission is built into the outdrive. Think of the outdrive as the transmission and the rear end of a car combined. To change the oil in the outdrive. First trim the drive until it is in a vertical position.Remove the oil vent screw ( large slotted head screw located on the upper port side of the outdrive) and the oil drain screw (located at the bottom port side of the unit). Let the fluid drain completely. Use lower unit gear oil (comes in a quart bottle that has a special tip on it to aid in adding the oil) and start filling from the bottom drain screw.Keep filling until oil starts to come out of the top vent screw(approx.2 quarts is required).Leave the bottle stuck in the bottom hole and take and re-install the top vent screw(This will prevent excess loss of fluid).Now pull the bottle out and install the bottom drain screw quickly. Remove the top vent screw and add oil until it runs out of the vent screw hole again...you do this because a little oil will be lost when you go to install the bottom drain screw back in. Periodically remove the top vent screw and top off the unit with oil.





By the way if this seems like too much of a hastle take it to a marina they will do it for about 40 bucks. Hope I have not confused you too much!Where do I put oil in for the gear shift?
First off, what are you trying to do?





Are you trying to check/fill the oil for your inboard engine? That should be obvious and easy to find on the engine block. There should be a oil cap on top or side (if V6 or V8) and a dipstick on the side. Some boats have a large enough bilge you can get under the engine and do the oil change the automotive way.





Are you trying to check/fill the gear lube for your sterndrive? (That's the part outside that has the prop stuck to it)





If so, then you first need to know the proper procedure to do it. If you don't do it right, expect VERY expensive repair bills.





Here is a web site that demonstrates the procedure:





http://www.nitroowners.com/projects/lowe鈥?/a>





I recommend this web site if you are interested in doing it yourself, otherwise take it to a reliable marine service shop.





Otherwise, if neither of these two is the question you have, please post an update with more details on your question.
What you are looking at is the power trim pump not a transmission.To fill it make sure the drive is down.On the left side of the trim pump about half way down you will see a large


slotted screw.Remove it and fill with 10w30.The hole is small,


so I suggest you use a squeeze bottle to fill it.(A ketchup or mustard bottle)This will make it much easier to fill.I hope this helps you.
If its a manuel transmion you fill it from under the car you put it strait in the transmition and it will prolly take 80w90 gear oil if its an auto matic you can pour it strait into the spout the dipstick comes out. The one that says 10w30 is prolly engine oil.