Ayuh,...... Welcome Aboard,..... How big is yer '86 Gibson houseboat,..??..??
I had a '69 Nautiline 12'x 34'er that I built a yard wagon for some years back,.....
I used 2 24' bar joists, spaced 10' apart, 'n a couple of ole house trailer axles under it,.....
I then lined the tops of the bar joists with 2x6 lumber to cushion it,....