I have a 19' skeeter zx 180 with a 175 merc. Currently it is trailered by a single axle trailer. Have had 2 bearing failures and I'm 99% certain that the weight of the boat is probably challenging the 3500 pound axle's capabilities. The axle is "true" to perpendicular in that the distance from the spindles to the coupler is equal. I am interested in anyone's thoughts or suggestions regarding the cost to replace my single axle trailer with a tandem... New trailer, used trailer, or conversion from my current single axle to a tandem axle and the costs?? Any suggestions would be appreciated as I'd like to have more confidence in pulling and the tandem axle would provide much more peace of mind. Thanks in advance!

It would be prohibitively high to try to add an axle. You should look for another trailer.

Your current trailer is fine, IMO. You may have issues with your current type of bearing lube system but I'd research that before I did anything else to eliminate that as a problem.
If you wanted to think outside the box you could look for an add on torsion axle rated at 5k to replace your 3.5k axle.

I replaced my axle about 2-3 years ago and made sure I added bearing buddies to ensure easy grease addition. The axle I just purchased (waiting on it to arrive for install) uses the already installed zerk so no bearing buddy is necessary. I'm really curious to learn more about this system as I've never had a trailer with this method of greasing.

I've seen more bearings ruined using a Buddy Bearing or something similar. Folks tend to overfill them, causing the rear seal to fail.

that may have been what happened. Looking forward to having the new to me type of greasing system.

+1

You either have bad luck or are doing something wrong. I have a Ranger 375 with a 175 Merc on a single axle OKT. Our boat weights are probably fairly close. It had buddy bearings from the factory. I have had this boat and trailer 30+ years and have never had a hub off.

I agree with the first bit about bad luck and/or doing something wrong.

Very much a skeptic of the 30 years on yours without opening them. Does the trailer sit in your barn with boat on a lift

I had a bearing buddy go out in Edna, TX at the walmart of all places (got out of the truck and the whole wheel was black from hot grease - wheel was spinning on the axle). Luckily it was on my 15 aluminum boat and they had the parts to replace the bearing in the store. It happened again on the same trailer in stockdale, and I had to leave it there and drive to floresville autozone to get a replacement. Now I keep replacement parts on hand when pulling that trailer. Seems like it's just prone to failure for whatever reason.

nope, I don't even own a barn and the boat and trailer do get used. I am on my 7th set of tires. Since it was built in 1985 I probably have some good ole American made bearings not some Chinese carp.

Quality wheel bearings that are properly maintained will last a long, long time.

Thanks, everyone, for your input. I believe that I was overfilling the hub with grease and the excess was going out the back as I likely caused the seal to fail. That was likely my culprit... my own efforts to try and prevent an issue actually caused an issue. I've got my replacement axle installed and am ready to go. Will be way more conscious of this issue as I now have the dexter grease zerk axle/hub.

Right... but where doe properly maintained fit into 30 years and never opened? I don't believe it. They have been replaced and someone forgot or that trailer doesn't move.

Had my torsion bar 3.5K axle for 18 yrs and replaced bearings/races and seals one time. I used Buddy bearings also. Proper PM is the key. Got an almost new complete TB 3.5K axle with 14" tires 4 sale now. 77563...I bought a new aluminum dual axle trl.last April, don't need the other trl (old EZ Loader). Tired of rebuilding it. Crossmembers...one BN never used,rear crossmember like new.

I'd buy a tandem, transfer the boat to the new trailer, and sell the old one. The only bearing failure I ever had was on a single axle, and quite frankly, a tandem tows way better.