Most marinas around our area measure from whatever bow appendage to whatever stern appendage for overall length. Appendages include dinghy, push/pulpit, davit, anchor, anchor roller, outboard, winches, wenches, sprits, ladders, steps, etc., etc., etc. whatever overall length the boat consumes within the slip. Slip fees are based upon boat length or slip length, whichever is greater. Overhang allowance varies by marina, but usually around 16" - 24" depending upon slip layout. Our boat measures 43' (after much discussion and deliberation with marina staff) in a 40' open slip, but the pile/bracket that secures the slip end adds another 20" to the actual slip length. Marinas becoming stricter on that allowance due to abuse/contact damage due to overhang. Several experiences over the years on this topic to some consternation.