How Full Should Boat Trailer Hubs be Filled with Grease

Published 11/26/2024

Question:

How full should the hub for a boat trailer be packed? I’ve read several conflicting stories. I have a regular hauling trailer as well. Would they be packed differently? I have an ez lube axle on my boat trailer and only plan to drive about 3 miles one way at 40 mph stop and go to launch. I’d rather keep the boat hubs pretty full to prevent water intrusion. Thx.

asked by: Duane

Expert Reply:

Hey Duane,

Once the bearings are packed with grease and the hub is on the spindle you'll need to slowly pump grease into the spindle until you see it start to seep out of the outer bearing. Be sure to use a manual grease gun so the grease doesn't fill the spindle too quick and blow out the seal.

This will be the same process for both your standard trailer and your boat trailer. I'm attaching a helpful article on replacing bearings that goes over this as well.

expert reply by: Jon G

Duane

11/26/2024

WOW! What a fast response. Very detailed article as well. Thank you. The article outlined that grease should be applied until the spring (assume bearing buddy) starts to move. Would that imply there is no air gap between the outer bearing and the bearing buddy? Since my system pumps from the rear bearing, and would eventually seep out the front, do I still leave the cavity area in my simple bearing cap (not a bearing buddy) completely empty? Or should a percentage of that cap be filled? Some articles implied filling the cap would keep water from being “sucked” in as the hub enters the water. Other articles warned about expansion due to heat thus blowing out the rear seal. Your advice implies leaving the bearing cap empty, correct?

Jon G.

11/26/2024

@Duane Bearing Buddy's are a little different, that's correct. Since you have a simple bearing cap you'll just leave it empty. I get where you're coming from when you talk about filling the cap to help keep out water, but it does open up the possibility of the grease seal being blown out the back of the hub so we tend to avoid advising that.

Duane

11/26/2024

@JonG Awesome. So I can fill the cavity between the pre-packed bearings via the EZ lube axle feature then the empty cap will serve as a type of overflow area for any sort of viscosity or heat-related changes with the grease. Got it. Thank you very much for the follow up, Jon.

Jon G.

11/26/2024

@Duane Exactly. You're welcome! Happy Thanksgiving!