If it's a Jon boat, it shouldn't be that heavy, probably around the same weight of a PWC. What about finding a used PWC hoist or making one along the same design? A neighbor has two that attach to the side of their pier and they just crank the PWC up out of the water.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).