Trailer bearing temperatures

[Jerry D S23 MI]

I'm prepping my boat trailer for the trip to the North Channel later this month, a distance of 500 miles.  I have not done any bearing maintenance for 4 years as it is a relatively short distance to the slip and each year was 1 trip to launch in the spring, 1 trip to retrieve in the fall.  So I pulled my bearing buddy caps off to see what the grease looked like.  3 looked beautiful, one looked like chocolate syrup .  I pulled that hub off, cleaned the bearings, packed them and reassembled filled with grease.  The others I just pumped a little additional grease in. 
    Took it for a 20 mile ride and then measured the temperatures of the 4 hubs;  they were 85, 85, 88, and 95.  Should I be concerned about the 95 deg hub or not?  (It was a hub that I just pumped more grease in).  Any thoughts are welcome on this....

[Wyb2]

New here, but maybe check your axle nut. 

On a (non-boat) trailer I over tightened an axle nut, and that bearing would get hot to the touch (guessing 120/130) at highway speeds.  In about 3 hrs of driving it turned new grease pretty dark in color.  I loosened the castle nut by one notch and added new grease and it's been fine since.

[Charles Brennan]

Jerry D, You listed 4 temps, so we can assume this is a tandem trailer we are discussing.  Most tandem trailers also have brakes on at least one axle, depending on the regulations for the state you tow in.
Did the one hub that was above average temps (compared to the other 3 hubs) have brakes? 
If so, the brakes on that particular hub may be closer in adjustment than its' counterpart on the opposite side of the trailer, (or possibly dragging) causing the hub heats to be higher.

Otherwise, I would agree with Wyb2 that the axle nut is slightly over-tightened.
I have a procedure for setting the axle nut that is less subjective than "finger tight".

1) Tighten axle nut to 50 lb/ft with a torque wrench.
2) Using the torque wrench as an indicator, turn wrench exactly 90º counter-clockwise, PLUS the next open notch, if the 90º mark is not evenly on a notch.
This is far more repeatable, than the vague "finger tight" advice.
(Got this information off a Timken Bearings web site.)

Another thought after reading your post:
Did you check for a possibly leaking inner seal?
That might help explain the "chocolate syrup" appearance.

Hope this helps,
Charles Brennan   

[Charles Brennan]

Wyb2, Your statement:

bearing would get hot to the touch (guessing 120/130) at highway speeds.

Is very close to the mark!
For most people, tolerance of pain is 135ºF and is the point at which you can touch a surface, but cannot keep your hand on it.

Since trailer wheel bearing grease typically fails (depending on type of grease used) at 500ºF - 700ºF you REALLY don't want to put your hands on a failed bearing! 
Tends to leave behind fingerprints.

This is why I am a Big Fan of infrared laser thermometers to measure my hubs.

Hope this helps,
Charles Brennan

[Jerry D S23 MI]

Reverend (!) Brennan (Esteemed senior pastor of the Trailers Church)
     I have been an astute follower of all your trials and travails over the last 25 years or so in the trailering side of sailing, so I was hoping you might chime in.  It is a non-brake axle hub that is the warmest, so I will follow your advice and then test it.  The inner seal is not leaking, BTW.
Thanks
Jerry