Marina & Boat Storage Acquisition & Underwriting Financial Model — Slip-Mix, Seasonality & Fuel-at-Margin (Excel + Google Sheets)

Buying a single marina or boat-storage facility — and need to know whether the deal actually covers its debt through the winter? Every other marina template takes one annual occupancy and one flat slip price and multiplies, and counts the fuel dock at gross — hiding the two facts that decide a marina deal: a slip is priced by the foot, and a busy fuel dock pushes huge gross dollars at a thin spread. A marina lives or dies on its slip mix, its season and a defensible fuel margin. So this model builds your income the way an operator does.

Slip revenue is built bottom-up: four wet-slip length bands priced per linear foot per month, plus a dry-stack rack line, each run through its own 12-month occupancy curve, so the summer peak and the winter trough are both visible, not buried in one flat number. Fuel, service and the ship-store are booked at NET margin only (never gross), shown twice — at full value to the P&L and at the lender haircut to the DSCR — because counting fuel at gross can inflate the DSCR by 30-40%. An explicit dredging/seawall reserve sits above the per-slip reserve. Then it underwrites the purchase like an acquisition: price from in-place NOI and the going-in cap, the capital stack sized on the lesser of LTV and DSCR (on the haircut NOI), the unlevered yield-on-cost, the off-season cash gap, payback and a 5-year exit.

What it builds for your deal:

• Slip-Mix (per Linear-Foot) × Seasonality Revenue Engine — slip revenue built bottom-up from four wet-slip length bands priced per $/ft/month, plus dry-stack, each run through a 12-month curve. The default settles at 230 wet slips + 120 dry-stack racks, $1,569,988 of slip revenue (wet dockage $1,162,890 / dry stack $407,098) at a blended annual occupancy of 75.1% — while the peak month runs 100%.
• Fuel-at-Margin ancillary — fuel/service/store booked at NET margin ($784,994, ~50% of dockage), never gross, then lender-haircut to the DSCR (80% credit = $627,995 credited, $156,999 disallowed). Counting fuel at gross is the #1 way a marina pro forma flatters itself; this model refuses to.
• Explicit dredging/seawall reserve — a real, large, cyclical capital event ($200k over an 8-year cycle = $25,000/yr) that sits ABOVE the per-slip replacement reserve; the marina-specific cost most templates omit entirely.
• Off-season cash gap & winter storage — a counter-seasonal winter-storage line ($156,999) earns when the slips can't; even so, a 4-season marina runs a real monthly deficit in the weakest winter month (-$2,057 at the default), surfaced so you size the working-capital reserve.
• SBA 7(a) / Conventional + Northern / Sunbelt toggles — swap the LTV, rate, amortization and DSCR target (SBA: ~72% LTV, 25-yr full-amort, no balloon) and the whole occupancy curve (Northern collapses in winter, Sunbelt runs near-flat), with the loan always sized on the LESSER of the LTV cap and the DSCR constraint — on the lender-haircut NOI.
• 5-year P&L & NOI — NOI struck after a full-service operating stack (~58% input OER, ~61-63% all-in with reserves, not an annual-lease 40%), at SINGLE-ASSET level. In-place NOI $919,072 rising to $1,148,714 by Year 5 (a sober +25%, no hockey stick).
• Full acquisition underwrite — price from in-place NOI ÷ going-in cap ($10,211,914 at the default 9.0% cap, $44,400/wet slip), the capital stack, DSCR 1.32x stabilized (1.24x going-in), debt yield 14.1%, an 8.72% going-in yield-on-cost stabilizing at 10.90%, a conservative 5-year exit and a 1.95x equity multiple.

What's inside:

• 10-sheet Excel workbook (works in Google Sheets too — no macros, no add-ins, no external links)
• 20-page PDF user guide — quick start, sheet-by-sheet walkthrough, how the slip-mix × seasonality engine and the fuel-at-margin haircut build your numbers, how a lender reads your DSCR and yield-on-cost, the dredging reserve, the off-season gap, where to find the seller's real numbers, and a full FAQ
• START HERE sheet: your first underwrite in minutes, only amber cells to fill
• Slip-Mix & Rate Engine sheet — per-linear-foot dockage by length band run through a 12-month occupancy curve
• Ancillary (Fuel-at-Margin) sheet — the full NET line and the lender-haircut line, plus winter storage
• Setup sheet with editable SBA 7(a) / Conventional and Northern / Sunbelt preset matrices
• Benchmarks & Dashboard with KPI cards, a 5-year NOI trajectory, and sourced 2024-26 ranges

Why this one: every formula is machine-verified — the full calculation graph is recomputed by three independent engines (including Excel itself) before release, and the slip-mix × seasonality engine, the fuel-at-margin haircut, the dredging reserve and the toggles are all stress-tested. Honest by design: the levered return is leverage-amplified, so the return is execution-driven — the shoulder-season fill and per-foot rate growth over the hold, not financial engineering. The headline is the stabilized yield-on-cost, the DSCR, the going-in cap and the equity multiple, not a cash-on-cash flattered by leverage; fuel is at net not gross; the dredging reserve and the off-season winter deficit are shown, not hidden. Models that balance.

Educational planning tool — not financial, legal, tax or investment advice. Marina and boat-storage dockage rates, occupancy curves, the slip mix, fuel and ancillary revenue, dredging costs, cap rates and lender terms vary by market and season and change over time; property tax is commonly reassessed upward on a change of ownership, waterfront insurance is expensive and volatile, the water bottom may be leased from the state, and fuel revenue is largely pass-through. Validate the seller's slip register, rate sheet, fuel/store receipts and trailing financials and your loan terms before relying on any number.