This boat is different then my last boat, how do I access the nipple to grease the bearings? Do I have to take the bearings out also and grease pack them? i dont even know how to get the cover off. The past owner said it is grease not oil hubs. The boat is a 2002 ranger 175vs if that helps. do i have to take a rubber mallet and work the hub cover off or take off the wheel? Thanks to anyone that can help me.

I was under the impression that all Rangers from 1996 and newer had oil bathed hubs.  Hopefully a Ranger owner will come by this and help out.

Is that black piece in the center of the hub soft, if so they maybe be a Zerk under it.

or check this out http://www.ehow.com/how_4901026_change-trailers-wheel-bearings-hubs.html

Those are oil filled hubs, not grease.  Take the tire off and look on the hub for a small nut that you can only remove with an alan wrench.  

Grab a small container and place it under the hub. Unscrew the bolt and turn the hub so the hole is pointing down.  Let it drain.  Turn it back up and fill it with 50 weight oil.  Then clean the bolt and the threads in the hole, dip the bolt in a thread sealant, and screw back in.

You're done!  

Oh!  I almost forgot - don't fill it all the way back up with oil.  Only fill it about 1/2 to 3/4 full.  That leaves room for expansion.  You can break the seals if you fill it all the way up.

I'm betting the previous owner drained the oil and replaced it with grease, since thats what he says is in there.

Those should be CoolHubs ..... oil bath hubs ..... in a nutshell, if it ain't broke, don't fix it ...... even the dealers will tell you, if they aren't leaking, leave them alone.

Look around on the trailer frame.  Should be a tag indicating what style hub and then go from there.