As i had noted in a previous thread (someplace), we were in need of a new jack. I researched just replacing the Fulton 1600-lb unit with a new one. Ours has a welded on mount plate and the locally available ones were the u-bolt type. I did determine that the jack could be disassembled from the bolt-on backing plate and mounted to my weld-on mount (same jack either way, just assembled to one or the other mount plate).
However, I found the F2 online and was ... ummm ... mesmerized (is that sick, or what?).
The F2 comes with U-bolts for up to a 3" height frame rail ... of course, mine is larger.
Long story short ..... the F2 would require a fabricated mount, but I found it at West Marine for only $15 more than the standard unit (same as was original), with a $15 coupon I had. Well, deal done.
I fabricated a 3/8" thick mounting plate, drilled and threaded it for Stainless Steel 7/16 x 14 bolts, welded it to the original weld-on mount (cut the center mount/pivot bolt off first), primed & painted ...... mount the jack. This one run-on sentence took a full day....
Unfortunately, it started to rain before the paint was fully cured and made it wrinkle ....
The F2 is not only a great jack for any boat, but for a heavy application, it's really great. No wobble, no kind-of laying over a bit. Faster (and easier) cranking .... etc ...... AND NO CORROSION!!! Lifetime warranty too.
The 8" wheel makes a big difference, I can actually move the boat around on concrete. 
