I know this is an old thread, and it looks like the original issues have been addressed.
However, I wanted to chime in about Harbor Freight trailers!
The one that's pictured in the original post - that's a 48x48. I have one that I modified to be a single-motorcycle hauler by running a plank that hangs about a foot off the back and then runs all the way up the tongue with a wheel chock installed. It carries 600 lbs plus with no problem. I suggest you get the model with the 12 inch wheels. I did take a leaf out of the springs. Another thing that makes life easier is to install the axle on top of the leaf springs by flipping the u-clamps over. You will have to flip the axle as well. This makes the trailer ride 2 inches lower.
If you're looking for it to be a boat trailer, why not just start with the Harbor Freight boat trailer? I have one of those as well. I bought three 12" wheels for it (one for a spare) instead of using the supplied 8" wheels. Again, I flipped the axle over (made up the height difference of the bigger wheels) and removed a leaf from each spring. It's perfect as is for a 10 foot boat, up to a 12 foot boat. I have a 14 footer on mine so I used long 2x4s for the bunks so that the bunks could overhang the back and go all the way to the back of the boat. A 14 footer should really be on a bigger trailer IMO, but if you can find the odd size metal stock that fits around or inside the tongue (1-1/2" by 3") you can extend that by 2-3 feet and it would be perfect.
Then there's the 4x8 trailer. I had one, got years of use out of it, and sold it. Again, get the model that has the 12" wheels for longer bearing life and it also has a higher weight capacity than the 8" wheel model. I did not use the supplied nuts and bolts when I put this together. I bought stainless steel ones that are longer for the places where one bolt can go all the way through the c-shaped stock rather than the short bolts that are supplied to go one in top and one in bottom. Get all the pieces laid out in front of you and analyze where longer bolts can be used and use them in every place possible. This helps with rigidity.
The weak aspects of all Harbor Freight trailers are:
- the supplied hardware - I replaced it all with stainless nuts/bolts/washers. Friends' trailers who used the stock hardware had theirs rust within a year.
- the paint. Again, friends' red trailers rusted quickly. I sanded all components to all of my trailers and spray painted them with Rustoleum "hammered" finish spray paint before assembling them. My 48x48 is dark gray, my 48x96 was light gray, and my boat trailer is bronze.
- the 8" wheels on some models. Get the 4-hole 12" wheels for around $40 a piece from Harbor Freight or various other stores. *You may have to modify the mounting for the fenders to clear the bigger wheels.
- the ride height of the trailers. Flipping the axle over to the top of the leaf springs is a cure. *You may have to modify the mounting for the fenders to clear the wheels.
