The present invention comprises an arm structure adapted for a boat transportation carriage. The boat transportation carriage may include a first frame portion and a second frame portion, with a third frame portion adapted to interconnect said two frame portions. Said arm structure may include a vertical arm portion and a horizontal arm portion, with the lower portion of the vertical arm portion being adapted indirectly to to rest against a chassis of the boat transportation carriage and its frame portion for supporting vertical loads. Between the lower portion of the horizontal arm portion and the upper portion of said chassis or frame portion and in adherement to the vertical arm portion there rests a support plate having a supporting surface for supporting cooperation with the horizontal arm portion and this supporting surface is disposed within a chosen intermediate area of said horizontal arm portion.