Grease is grease right? Well, no, it's not. Over the years when I have been out of the Spartan Seacock grease I have tried everything from standard white lithium grease to expensive synthetic grease like Morey's Red or Amsoil waterproof synthetic grease. None of these wonder greases has worked nearly as well, or lasted as long, as the grease sold by Spartan Marine.
This white lithium based grease is THICK because it can be. Picture cold peanut butter and you'll have the consistency about right. Spartan has added some proprietary and "top secret" Tony the Tiger like ingredients that actually DO WORK. Trailer bearing grease is thinner, because it has to be. These valves only ever turn up and down maybe 60 times per year, they are not spinning at 70MPH while driving 100 miles to a boat launch ramp. Because these valves rotate less than a full revolution the grease can be significantly thicker for the application, and it just works.
Spartan is fairly adamant that you not use a synthetic grease and I can concur with their suggestion. Many Cape Dorian's swear by Morey's Red but I still find the Spartan grease to out perform it fairly handily. I find synthetics get hard, have less "film thickness" and the valves leak sooner and turn harder sooner than when I use genuine Spartan seacock grease.
The grease is about $12.00 for a tub that will last many years.