it's a good project. i've been involved in a few of these and i'll give you my take on the usual problem areas:
- axles have probably been submerged several or many times. depending on salt or fresh water, you'll definitely want to go over them and check for pitting/corrosion and repack. bearing buddies are a cool mod to add so you can just pump fresh grease into the bearings with a grease gun through a zerk.
- lights and wiring - same deal. depending on water and how often, may have to do a full replace.
- axle location if set up for a boat will be pretty far back since motor and gas tanks are usually in back of the boat. this makes for a very nice towing trailer (long tongue) but you may need to relocate forward as previously mentioned to get your 10% tongue weight. i would just recommend not going any farther forward than needed. if you know how you are going to load your tractor, you'll be way ahead of the game in getting this right. i can't emphasize enough how much your choice of axle location will affect the trailerability and ride of finished trailer.
- spring shackles will probably need new sleeves due to water submersion. also, check the u-bolts and centering tab for rust and replace as necessary.
- tires need to be carefully attended to. biggest problem with low mileage tires is dry rot from UV exposure. biggest problem with replacing them is finding the correct load range in the size rim you have. often times older boat trailers have the older and smaller sub-15" size rims. it's getting harder and harder to find these tires for the 14" and 13" rims. also, the less air volume, the less loading capacity on the tires. very important to match the load rating on the tires (x4) to the axle rating (x2) and ultimate load on the trailer. don't forget to subtract the actual weight of the trailer from the GVWH to get the actual size load you can carry. i weight my finished trailers empty at the local quarry scale (for free) to get my actual weight and finished capacity. tool boxes, gas cans and binding chains can add significant weight.
- if going with surge or elec brakes, don't forget that significant load shifts can occur during hard stops and your tire weight carrying needs to account for that (ie safety margin).
- surge brakes are notorious for leaking seals and low hydraulic fluid. at the least, you need to do a full fluid flush and replace with fresh fluid due to the hygroscopic nature of brake fluid. it's not the boiling point reduction so much as the rust on internal components from the moisture and breakdown of additives.
- carefully check out the hitch for wear, rust, etc. replace if necessary.
good luck and happy building!
amp
