Migrating Off Legacy Marina Software: A 90-Day Playbook

A marina software migration done in the off-season takes roughly 90 days: 30 days to export and clean your data while you finalize the new contract, 30 days to build and verify the new system in parallel while training staff, and 30 days to cut over billing, retire the old system, and prepare for spring. The work is real but bounded, and the marinas that struggle are almost never the ones with the messiest data. They're the ones without a plan and an owner.

If you spent this season fighting your software (the server in the office closet, the reports that need three exports and a prayer, the booking module boaters won't use), the off-season is the window. Peak is over, spring commissioning is months away, and the decisions you make at the start of the off-season determine whether next season runs on the same system that just fought you for six months.

Here's the plan we use, adapted for any destination system.

Before Day 1: three preconditions

1. A named internal owner. One person with authority and dedicated hours. Migrations without an owner don't fail loudly; they stall politely until spring makes them impossible.
2. A signed decision. The evaluation is done (if it isn't, start with the five questions to answer before you talk to any vendor and work through it properly first). Don't begin migration work "while we decide."
3. A cutover date tied to your billing calendar. The natural moment is just before you generate next season's renewal invoices, so the new system sends them and the old system never bills again.

Days 1-30: Export, clean, and contract

Export everything from the legacy system now, not at day 60. Customers, boats, slips, contracts, reservation history, open balances, payment history, notes. Two reasons for urgency: you'll discover immediately whether your outgoing vendor makes export difficult (budget time for support tickets if so), and every later phase depends on this data. If your legacy contract has termination requirements (notice windows, end-of-term dates), read them this week and calendar the notice.

Clean while it's exported. This is the highest-value grunt work of the whole project, and it's spreadsheet work anyone on your team can share:

• Merge duplicate customers (the same boater as "Bob Smith," "Robert Smith," and "Smith, R").
• Verify boat LOAs against reality; migration is the perfect moment to fix the under-measured lengths that have been quietly under-billing for years.
• Reconcile open balances so you migrate true receivables, not artifacts.
• Standardize slip naming (if Dock B slip 14 is "B14," "B-14," and "14B" in different fields, pick one).

Finalize the new contract with migration in it. Data import scope, training scope, a named implementation contact, and your go-live date should be in the agreement, not assumed.

Deliverable at Day 30: clean master data files, signed agreement, cutover date on the calendar, staff informed of the plan and their part in it.

Days 31-60: Build in parallel, train on your own data

The new system gets built and verified while the old one keeps running. Nothing customer-facing changes yet.

• Import and verify. Load the cleaned data, then verify like an auditor: pick 20 customers at random and check every field against the old system. Sum open balances in both systems; they must match to the penny. Walk the slip map against the physical docks.
• Configure your business rules. Rate schedules (per-foot, seasonal, transient, metered utilities), late-fee policy, deposit rules, tax settings, document templates. This is also the moment to fix policies the old system forced on you; the workarounds you've been living with don't need to be migrated.
• Train on real data. Staff training sticks when people see their actual customers and slips, not demo data. Run each role through its daily tasks: take a booking, post a payment, check in a transient, run end-of-day. Short sessions, repeated, beat one marathon.
• Dry-run the critical path. Generate next season's renewal invoices in the new system in draft. Compare a sample against what the old system would have produced. Every discrepancy found here is a customer phone call avoided at renewal time.

Deliverable at Day 60: verified data, configured rates, trained staff, and a successful invoice dry-run.

Days 61-90: Cut over, reconcile, retire

• Pick a quiet cutover moment (a Monday in the deep off-season). From that date: all new transactions, bookings, and payments in the new system only. Double-entry periods longer than a few days are where migrations go to die; a hard cutover with a verified system beats months of parallel keying.
• Send something real immediately. The renewal invoices, or a season-announcement email with portal login instructions. A live system with real traffic surfaces the last configuration gaps while there's still time to fix them calmly.
• Reconcile the first close. At the first month-end, reconcile revenue, receivables, and deposits between the new system and your accounting. Then do it again the next month. Two clean closes means the migration is actually done.
• Retire the legacy system deliberately. Keep a final complete export (and read-only access if offered) for your records-retention window, confirm the termination per your notice requirements, and stop paying for it. If the old vendor's pricing included per-booking or processing fees, note what your first-season savings look like; that's a number worth knowing.
• Launch the boater-facing pieces before spring. Portal invitations, online booking live, autopay enrollment in the renewal packet. Cutover in the deep off-season means boaters meet the new experience at spring commissioning with zero mid-season risk.

The one-page version