Still tuning up the merc 35 outboard. Does the lower unit oil have a level indicator at all, or do you just fill it up to the fill hole? What kind of oil are you guys using? Like automotive gear oil?

There will be a drain hole and a vent hole. Pull both plugs, fill from the drain plug until it comes out the vent hole. Work the prop shaft back and forth and make sure you get all the air out from the gears. You should be golden. Just make sure you don't loose the plug gaskets when you take the plugs out.

Dont mean to hijack the thread but Mike can the gaskets be reused and if so how many times?

What kind of pump do you guys use to fill it from the drain hole?

If you go to a marine dealer you can buy the proper type of lower unit lube. For another $10 or so you can buy a pump that will last you a lifetime.

Use the tip that comes with the bottle. Squeeze it in by hand until it comes out the top vent hole just like Mr. Mike says.

the gaskets can be used again, but is always recomended to replace them each time, just like four stroke oil drain gaskets, esp. suzuki. and at 50 cents each, go to the boat shop and buy 10 of them.