If you don''t want to remove the boat from the trailer, you don''t have to. It is not very difficult to clean and paint
a boat bottom while it is on a trailer. The key is to raise the boat a few inches and move the trailer back and forth a few feet. If you do want to remove the trailer entirely, it takes just a little more work.
With the understanding that I''m simply relating my own experiences, that I''m not suggesting that anyone follow my example, and that no liability will attach to me, read on.
Most boat trailers I''ve seen are just open web frames with pads or rollers to support the boat. I used to have a MacGregor 25 and whenever not in the water, it sat on its trailer in my back yard. To raise it from the trailer required 8X8X16 concrete blocks, several 2X10 planks, a few 2X4s, a few scraps of plywood, and a small hydraulic jack; the "bottle" type.
This is how I did it. I selected a storage spot where the earth was fully settled and had not been disturbed for at least a few years.
With the trailer located in its "permanent" position, I lowered the tongue so that the stern of the boat was raised about 6 inches. Using 8X8X16 concrete blocks, I built 3 "towers" to support a doubled 2X10 against the now raised stern of the boat. I started with two blocks touching, side by side. The next course of blocks was placed perpendicular to the first course and succeeding courses were alternated. I placed them as close to the rear of the trailer as I could without interfering with any of the boat''s running gear. Because the boat''s bottom was not flat, I placed some pieces of 2X4 away from the centerline as blocking, to prevent the boat from rolling to one side or the other.
I then raised the trailer tongue and the aft end of the boat lifted from the trailer. I took a walk around the boat and gave it a few good shakes to ensure that it was stable.
Finding a spot along the centerline of the boat in front of the keel about 18" to 24" in front of the forward trailer cross-bar, I built a block tower tall enough to support the jack (in its recessed position) and a wooden pad beneath it, and another one on top (to spread the load) close to the bottom of the boat.
I pumped a few strokes to ensure that the jack was properly placed. If it was, I proceeded. If it wasn''t, I shifted it until it was. When the jack was properly placed I pumped it just until the weight of the boat was transferred from the trailer to the jack. Again, I walked around the boat and gave it a few good shakes to see whether it was stable. I then pumped the jack until the boat was several inches off the trailer.
Now, I was able to move the trailer until the crossbar reached the jack tower.
This provided me with sufficient maneuvering room to do whatever bottom work was necessary. If I had to remove the trailer entirely, I would build another block tower, behind the forward trailer crossbar. Then I would lower the jack until the weight of the boat rested on the second block tower. The jack and its block tower were removed.
The trailer was now moved until the next crossbar reached the block tower. In my case, this crossbar was the axel.
Next I rebuilt the first jack tower in front of the second block tower. I pumped just enough strokes to transfer the weight of the boat from the second tower to the jack tower. I walked around the boat and gave it a few good shakes to ensure that it was stable. Then I pumped a few more strokes to raise the boat a few inches from the second block tower.
Next I removed the second block tower from in front of the crossbar and rebuilt it just behind the crossbar. I lowered the weight of the boat to the second block tower. When I was satisfied with the boat''s stability, I removed the jack tower. Now the trailer was moved completely from under the boat and the boat was supported on the block towers.
Additional bracing was placed to ensure complete stability.
Getting the boat back on the trailer was a simple matter of reversing the steps.
The beauty of the procedure is that the boat is never raised more than a few inches from the trailer. As I recall, an 8 ton jack cost about $20 ten years ago.
Trying to describe a procedure such as this often leaves much to be desired. If you have any questions, you may wish to e-mail me directly at email@example.com.