I have bravo one's with 502mpi's. I dont see the top fill/vent plug. I guess the drain is behind the prop. Any instructions for me, this is my first time,lol. How much oil does each drive take? Thanks alot

Everything you need to know right here.....

http://www.sterndrives.com/changeyourbravogearlube.html

Thanks alot

On a side note, it takes a very long time for the oil to fully drain. Some even leave it overnight to fully drain. Bring lots of rags because you are likely to make a mess.

Yup! And, you (brian 18330) have twins, so buy two oil drain pans so you can let them drain together, because it does take a loooooong time.

Try to do it after you run the boat and drives (oil) are still warm.
Look out for the thin cardboard gasket on the drain plug, they often stick to the drive and end up in the drain pan.
Merc racing makes them with o-rings which I prefer over the cardboard.

anyone have the part number handy for the o-ring style?

Stick with the gasket type. Merc stopped installing the o-ring type a while back because they had problems with the vacuum from the propeller pulling gear lube past the o-ring.