1 Baywood Marina, located in New Jersey, offers slips that range from $1,200 to as much as $4,400 for the year. 2  For example, a boat that is 15-19 feet will cost $1,200 for the year, while a boat that is 33-36 foot boat can cost $4,175.3  Standard boat slips should include a 30-amp (or greater) electric hookup and water. On average, for a boat between 30 and 40 feet, you should be prepared to spend anywhere from $150 to as much as $950 for a boat slip. 2  Again, since there are so many variables, it is extremely hard to pinpoint an exact price.