Bad bearing seals?
 

A few weeks ago I trailered the boat 100 miles round trip to get an estimate for some work. My usual trailer trip is 1.5 miles round trip to the ramp. I topped off the bearing grease before the trip with enough grease thru the Posilube fittings to push some of the old grease out. Today I was checking on the trailer and noticed these grease spots on the hull. The port side was clean. Do I need to get the seals changed? If the seals need to be changed I'll probably go ahead and change both hubs. The grease spots were about 5 feet long, so I think both hubs are involved After paying for labor, possible new bearings and seals I can get a new hub for about the same $ and have new stuff.

What’s wrong with the hubs? If you get a package (hub, bearings, and seal) you can do it yourself in an hour. Depending on conditions, the grease seal and races can be a pain removing in my previous experience.

“I topped off the bearing grease before the trip”

That is why the seal leaked. Seals last practically forever except for those dedicated to topping the bearing grease before a trip.

When you added more grease, did you also wipe some away when it oozed at at the front of the hub? If not, you filled up the front dust cover with grease and then the grease got hot when the trailer was rolling and found the path of least resistance out of the hub.

When greasing, remove the front dust cover entirely, not just the rubber plug. Then pump in grease and wipe away the grease that oozes out of the outside bearing before you reinstall the metal dust cover. The air space in the dust cover gives room for the grease to expand into once it warms up and is under pressure from the spinning bearing.

To paraphrase the first law of thermodynamics, grease is neither created nor destroyed in a hub, it is changed from one form to another. You added grease and it had to go somewhere once it warmed up!

I push half a tube a grease through my hubs with an electric grease gun every few weeks. That process does not cause me any leaks. Dry seals, on the other hand, can crack and cause leaks.

I'd say your seal is no good.

Seals, just like your windshield wipers are made from rubber compounds. Just like your windshield wipers, seals don’t work very well, nor last very long, without lubrication.

Windshield wipers don’t last forever, neither do oil seals. All rubber compounds are not the same, so the quality of your windshield wipers and oil seals effect their performance and life expectancy.

My guess is you didn’t pump out all the bad grease. Instead, you pushed the old runny stuff to the top.

The spray pattern is indicative of water logged grease. Fresh grease wouldn’t splatter so easily or be black.

Also a good idea to spin the hub when adding grease to posi lube hubs

The grease seals are bad, or the mating surfaces for them are pitted out, or both.
Pull the hubs , clean up the spindles , and see what you have there. Pump new grease thru the spindle to flush out the old.
I like the superlube grease, clear and salt impervious , clear grease will show nastiness when pumping thru.
You don’t get grease flinging out of them by just loading the fittings.

I prefer replacing the hub verses rebuilding the old one.
This way you get grease loaded bearings with new races, new seal and new lugs with nuts. Nicely painted and ready to go.

I'll probably do all 4 hubs new with preloaded bearings. I found a place with Timken bearings for reasonable price.

https://www.trailerpart.com/p-9191-13hlb1e-tk.aspx

I had a spindle with a SS speedy sleeve develop rust under the speedy sleeve which distorted the sleeve the seal rode on causing a leak.
need to make sure you inspect them all when taking apart and cleaning them for the new hub install