Go and get a pump and do this the right way, if you do not, you will burn up your upper gears and cost yourself a couple grand at least. It is a closed system once all the drain/fill plugs are installed. Whatever the capacity of the drive is listed as you must get that much oil in it.
PS
there's more than one OMC Cobra drive, the original from 86-93, then the new joint venture series from 94 and up (same as a Volvo SX) the procedure for each is specific to that drive, so you need to know what the correct procedure is for the one you have.
this is how you fill the original series, not from the very bottom like a Merc but from the second hole up, with the dipstick just laying in the top cover hole (this allows air to escape) get 2 qts in, then check with dipstick, if you need to add some you can add from the top. Pump slowly to allow air to escape. Then retighen dipstick. Also replace the fiber washers each time you change the oil. This one has 20+ years of salt water use and shifts like new, as bad as it looks!
PS a '94 could have either drive, the power package sometimes can be a year older than the boat itself. The original like this one is flat across the top of the upper gear housing, the later joint venture style has a hump on top same as a Volvo SX.
