How to Keep a Ship's Log: What to Record on Every Leg (and Why)

A ship's log isn't ceremony — it's the maintenance record, fuel history, and memory of your boat in one place. Here's what belongs in each column, and how to make the habit survive contact with a busy helm.

Jul 3, 2026 · 7 min read

Why keep a log on a boat that doesn't have to

Recreational boats in the U.S. aren't required to keep a logbook — that obligation belongs to inspected and commercial vessels. So every recreational log, from a center-console to a trawler, is voluntary, which is exactly why the ones that exist are useful: nobody keeps one for a regulator. They keep it because the boat pays them back.

The payback comes from three directions. Maintenance: outboard and diesel service lives are scheduled in engine hours — most manufacturers put the routine service interval at roughly every hundred hours or once a season — and the hour meter only tells you where you are, not when you crossed the last interval. A log does. Money: a documented history of hours, service and fuel behavior is the difference between an asking price and a defended one when you sell, and a clean answer when an insurer or warranty adjuster asks how the engine was run. Diagnosis: fuel numbers drifting leg over leg — more gallons for the same run at the same speed — are how fouled bottoms, tired props, and injector problems announce themselves months before they become obvious.

There's a fourth direction the spreadsheet crowd undersells: it's the memory of the boat. Which anchorage held in that southeast blow, when you crossed to the islands and how long it really took, the leg where the genset finally gave up. Sailors have kept logs for centuries for navigation; on a recreational boat today, the navigation is handled — the log is for everything the chartplotter forgets the moment you power it down.

The columns that earn their place

A working log is one row per leg — dock to anchorage, anchorage to marina — not one row per day. Cruisers who live aboard for a season converge on remarkably similar columns, because each one answers a question that actually comes up later:

  • Date, departure port, arrival port, and where you ended up (marina, anchorage, mooring, haul-out) — the skeleton every other question hangs on.
  • Depart and arrive times — trip time falls out of these, and with distance it gives your real average speed, which is the honest number to plan the next passage with (not the brochure cruise speed).
  • Positions (lat/lng) at departure and arrival — settles "how far is it really" arguments, and reconstructs the season's track when you want it.
  • Distance in nautical miles — logged by you, not inferred. A straight-line number between positions understates a real route around shoals and headlands.
  • Engine hours per engine, at departure and arrival — the column doing the most work. Per engine matters on twins: uneven hours are how you notice one engine is carrying the boat.
  • Genset hours, if you run one — generators eat service intervals quietly, at anchor, while nobody is watching a helm display.
  • Fuel per tank at departure and arrival, plus fuel added — depart-minus-arrive is the leg's true burn; tracked per tank it also catches a list-inducing imbalance and the slow mystery of a tank that reads lower than the math says it should.
  • Notes — the column that turns a table into a log. Weather that mattered, what broke, what worked.

Paper, spreadsheet, or app — honestly

Paper is the traditional answer and still a good one: it needs no battery, survives spray in a zip-lock, and writing at the helm cements the habit. Its cost is everything downstream — you can't sum a season's engine hours or graph a burn trend without transcribing, and most paper logs are never transcribed.

A spreadsheet is where most serious logs end up, because columns of numbers want to be sorted and summed. The classic cruiser's sheet — a row per leg, colored column groups for engine hours, genset, and fuel — is genuinely powerful. Its cost is at the other end: data entry happens hours after the fact, from memory or phone photos of gauges, and the arrive-time you type at the marina bar is softer data than the one stamped when you actually tied up.

An app's case is narrow but real: it's the only format that can capture the fiddly numbers at the moment they're true — the clock, the position, the hour meter, the tank level — and still hand you the spreadsheet later. The honest caveat is the same one we apply to everything: captured data is only as good as its source, and a log the app writes for you is worth checking with your own eyes before you trust it for a service decision.

The habit that makes it stick

Logs die at the transcription step, so the fix is to never have one: record at the two moments the numbers are in front of you — castoff and lines-secured — and record less rather than nothing. A row with only times, ports and engine hours is a real log entry; a perfect twelve-column row you meant to fill in Sunday is not. The pre-departure minute you already spend checking fuel and the engine (the same minute as your pre-departure checklist) is where the departure row starts; the first quiet minute after arrival finishes it.

How Far Enough does it

Far Enough's Logbook keeps the ship's log alongside the trip log and fill-up history — one place for every record the boat generates. A log entry carries the full working set above: ports, times, positions, logged distance, per-engine hours, genset hours, per-tank fuel with fuel added, and notes, with trip time and average speed computed from what you enter.

The at-the-moment part is two taps. Start leg stamps a new entry with the departure time — and, if your boat's network is connected (live NMEA 2000 / SignalK data), the position, engine hours and tank level straight off the bus. The dashboard then shows the open leg — where you left and how long you've been underway — until End leg stamps the arrival the same way and hands you the entry to finish: arrival port, where you ended up, anything for the notes. No boat network? Both buttons still stamp the times and your home port, and the rest is normal log-keeping.

The export is the spreadsheet you'd have built anyway: one CSV with a column for everything — day and date, destination type, both ports, both positions, trip distance, time and average speed, depart and arrive hours for every engine, genset hours, and depart/arrive/added fuel for every tank — ready for Sheets or Excel. Two honest limits: boat-network capture reads one engine's hour meter (fill the second engine's column yourself, like a paper log), and the log lives on your device — the export is how it leaves, which is exactly how we think a private record should work.

Far Enough's Logbook with three ship's-log legs, and the exported CSV open as a spreadsheet with passage, trip and engine-hour columns
The Logbook keeps every leg; the export is the spreadsheet you'd have built anyway — a column for everything.
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How to Keep a Ship's Log | Boat Log Book Guide · Far Enough