Steering component grease
I've been using Sta-lube Premium Red for a while but there's a lot of good choices available.
First, make sure it meets the basic requirements spec'd in the shop manual. In most cases thats not too difficult.
NLGI Chassis Rating: LB is common ( its rating for the joints)
NLGI Consistancy: 2 (this is how thick it is)
EP (its designed for Extreme Pressure)
If its going to see water (pulling boat out) then that's a special factor to look for (washout rating and so forth).
Greases are made from an oil and a thickner that retains it (plus additives).
When replacing an existing grease use one with a compatible thickner. Most current chassis greases will be Lithium Complex or Aluminum Complex.
Here's a hot link to a compatibility chart