Combine Harbor Freight 4x8 trailer with the HF Boat Trailer

Article By Shorty
I probably should first explain why I did this project. I was about to make a major move across the country, and had decided that the way we were going to do it would be to pack all our household stuff in PODS units and then drive my family in my car, pulling one boat trailer with our bare essentials and my koi fish in a tank, in the boat. I have an old junky powerboat hull that was perfect for this job, the original floor on it was completely trashed and I was replacing it with a simple, open flat plywood floor and was just perfect, the only problem being that the trailer that the boat was on couldn't carry the weight of the boat plus my fish. Just so happens that Harbor Freight has a 4x8 utility trailer with a heavy steel frame, and a rating of 1800 lbs, which is just enough for my purposes. The problem is the 4x8 utility trailer wasn't long enough, so I needed to fabricate some kind of tongue for it.

I thought about lots of different options, but then a really simple one dawned on me. I had a harbor freight boat trailer, which does have a long tongue on it, but did not have a heavy enough axle and springs. The only stuff I carry on that trailer is either light boats, or small loads.

So I came up with the idea of cutting the tongue off the boat trailer, and adding it to the utility trailer.

I set it up on the garage floor, and it looked like it would work great. After the move was over, I'd then rebuild the leftover frame and axle into a simple "stick" type trailer that I could use with my light boats.

And here it is, the moment I crossed the point of no return on this project.

To get the tongue on the new frame straight, I used a boat building trick and measured from the tip of the tongue to each corner of the frame. Then I welded along every place that the new and old frame touched each other.

The only thing that bugs me about this modification is the short distance that the old frame overlaps the new one. The short tongue that came with the utility trailer mounts in the exact same place, so it should work OK, but I can see it would have been better to just buy a couple of 20' sticks of 2" x 3" rectangular steel tube, and weld on so the tube would extend the entire length of the utility frame.

I have a bit of a problem with my dogs chewing on the wires, so I added a tube in the transition point between the two frames, so the wires could hide in there.

Another exposed wire area is where the wires come out the side of the frame, and run out to the lights which are mounted on big angle brackets. So I added a small piece of pipe to the angle bracket to protect those wires.

Next were the brackets to hold up the bunk boards. I wanted to keep the utility trailer with it's flat bed, and have brackets to hold the bunk boards so I could later remove the bunks and carry various loads on the flat bed.

Added all the parts and here is the test crew making sure I got everything on there.

Before I could get the boat on, my new koi tank arrived and I had to pick it up from the shipping company. So the trailer made a quick trip down the road and carried it's first 1200 lb load.

Back at home, time to cut the bunks so they match the hull. Here is how to meausure and cut the bunk boards

Got the bunks cut to match the hull, after this picture I added some carpet.

Not a very good picture, but the power boat is up on the new trailer.

Soon after I got the trailer to this point, the move got cancelled.

It is nice that I have a new trailer though, and in the end it was cheaper than fixing up the old trailer that came with the boat -- I would have had to do a full fixup on that old one: tires, bearings, weld on repairs, new lights, find a spare for it, dolly wheel etc.