Less certain, at least on a cruising sailboat, is whether you need to remove old bottom paint to improve boat speed. Old paint does indeed add weight to your boat, but even 20 years' worth of residue adds only a marginal amount of poundage to the boat's overall weight. More likely, old bottom paint will result in an uneven surface, which increases drag as the boat moves through the water. But calculating the toll of imperfections and weight is dicey at best, and it may be of marginal importance to a long-distance cruiser. In short, how much labor and money do you want to invest to gain, say, a quarter of a knot of boat speed? For racers, the answer's easy: Take off the old bottom paint; toil and cost be damned. For some cruisers, however, a quarter of a knot may not be worth the effort and expense.