Then ADD the other known weights such as FUEL and FRESH WATER, WASTE WATER and GREY WATER TANKS etc.
(multiply the total Gallons X 8 Lbs. to get the estimated weight)
Then ADD 2,000 lbs. to cover EXTRA GEAR, BATTERIES, and other Misc. items that may be on board. This "buffer" weight will also help cover Rough Water conditions (from weather or traffic) and allow your lift to raise high enough to get your LOWER UNIT up out of the water and have virtually ALL of the steel on the lift, ( with a Fiber Steel Boat Lift ) above the waterline also. This will help keep it Clean and greatly lengthen the life of the lift.
When you add these weights together and get your total , make sure your lift can handle this weight.