So, I got an answer from Myco and it was what I had suspected. Myco trailers (mine included) as of 2006 have air-tight hubs; no water or other contaminants enter the hub chamber so the grease remains sealed within the hub and cannot wash out. Makes sense. For non-airtight hubs, other products might be better.

While we're on the subject, I also have one of these:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It ain't cheap but was a life-saver having to pack 12 bearings and fill hubs.

Ive always used red and tacky

I'm a little confused. Aren't all boat trailer hubs water tight? I wouldn't want any water inside of the hub, it would destroy the bearing. Amy signs of water intrusion and it is time for new seals.

Power grease guns are great, but make sure you don't pump the grease into the hubs to fast, you can blow the seals out.

I use the Mystic red grease on just about everything.
And I also have had and used a version of that bearing packer for longer than I can remember; it's a great tool.

I would assume so, but another poster was talking about "wash out". Myco uses an "air-tight" hub, that has a special bushing on the axle, a viton grease seal on the rear of the hub and a rubber diaphragm on the grease cap that allows the hub to be pressurized with air to keep everything out. The grease seal and the grease cap are also coated with a bonding agent prior to being pressed into the hub to maintain the air pressure.

Yeah, I know. The Dewalt has a variable speed trigger; allows a slow and steady pump. Takes a while but a hell of lot easier than pumping that grease gun handle a few hundred times.

That's the stuff! When you get it on you it is very hard to wash off

X2 on the 221 Schaeffer. Take whatever you think you want to use and put some on your fingers and run under water, pretty easy to tell how your grease will hold up.