Before you sign, every screen has to show you something true. Check each instrument against something you can see, set it up for your week, and learn the radio while the technician is aboard.
1 · Chartplotter
A chart for every mile, a fix you have checked
What should I check on a charter yacht's chartplotter before I sign?
That the chart card covers the whole cruising ground the contract allows and is recent, and that the plotter has a fix showing the boat on its berth. Without satellites it shows its last stored position.
Ask of the chart card: does it cover the whole cruising ground the contract allows, and how old is it? A base map without depths is not a chart. Paper chart and pilot book are the backup and hold the harbour detail: ask for current ones.
Without satellites the plotter shows its last stored position.
Wait for the fix and see the boat on its berth. GPS positions are on the WGS84 datum; an older paper chart on another datum prints the shift to apply.
2 · Plotter set-up
Make the plotter yours before you leave
How do I use the MOB button on a chartplotter?
The MOB key drops a mark and shows the bearing and distance back to it. Keep it for a person overboard only: mark an anchorage with an ordinary waypoint, because on some sets MOB also sends an alert.
Setting
What you want
Units
Nautical miles, knots and metres, as on the chart
Night palette, dimmer
Found and tried in daylight
Routes, waypoints
The last crew's cleared, your own built from the chart
Track
Where you have been: your way back out in the dark
MOB key
Drops a mark, shows bearing and distance back to it
Have the technician show how MOB marks and clears, then brief the crew. It is for one thing only: an anchorage is an ordinary waypoint, and on some sets MOB also sends an alert.
3 · Depth, speed, wind
Know what each number is measured from
At what depth sounder reading does my yacht's keel touch the bottom?
With no offset the sounder reads below the transducer, not the keel: with a 2.1 m draught and the transducer 0.4 m down, the keel touches at a reading of 1.7 m. Set the shallow alarm a metre or more above that.
Compare the sounder with the harbour plan. A reading three times too big is in feet. With no offset it reads below the transducer, not the keel: with a draught of 2.1 m and the transducer 0.4 m down, the keel touches at a reading of 1.7 m. Set the shallow alarm a metre or more above that.
The log is a paddle wheel, speed through the water; SOG is GPS speed over the ground. The difference is current, and a log at zero under way is a fouled wheel. Plan arrivals by SOG: 24 miles at 4 knots is six hours.
A wild wind reading in a calm is often a halyard round the masthead unit. A number missing at one display but shown at another is the network, not the sensor. On a catamaran ask which readouts repeat at the second helm.
Rule
A dead instrument goes on the form as unserviceable, so it is not charged to you. Weigh it against your plan: no depth, no anchoring; radar matters at night and in fog.
4 · Compass, paper, log book
What still works when the screen goes dark
How do I check the compass deviation on a charter yacht?
On the test run, with no current running, compare the steering compass with the plotter's course over the ground: whatever variation does not explain is deviation, often from a phone by the binnacle.
Compass 090°, plotter 098° true: 3°E is variation, the other 5°E deviation.
On the test run, with no current running, compare the steering compass with the plotter's course over the ground. What variation does not explain is deviation, often a phone by the binnacle. A hand-bearing compass has no deviation card: use it at the bow, away from iron.
A tablet is a backup only with offline charts and a 12 V lead. A phone app is a third source: it overheats, goes flat, and its depths may be unsurveyed. Keep the log book daily: times, positions, engine hours, weather, breakages. From the briefing take the local wind and the currents in channels.
5 · Autopilot and AIS
Helpers that still need a lookout
Does my charter yacht's AIS show me to other ships?
Only if it is a transponder: a receiver shows the ferries to you, but only a transponder shows you to them. Ask which the boat has, and for a night passage set a CPA alarm audible at the helm.
See Standby, a course change and the alarm on the test run. The autopilot steers a heading, not round boats: in harbours and anchorages a person steers. In wind mode it holds the apparent wind angle, so it follows every shift: watch the course. If its heading disagrees with compass and plotter, the base calibrates it.
Ask whether the AIS only receives or is a transponder: a receiver shows the ferries to you, only a transponder shows you to them. For a night passage set a CPA alarm wide enough to act on and audible at the helm.
6 · VHF and DSC
Set the radio up and learn its keys
Which VHF channel should I use for a radio check?
A working channel, never channel 16, which you keep watch on under way. Call a station miles away: a check across the pontoon says nothing about the antenna.
Under way you keep a watch on channel 16, with dual watch on the base's channel and the squelch just above the hiss; in harbour the set may go off. Make the radio check on a working channel, never on 16, with a station miles away: across the pontoon it says nothing about the antenna. Use 1 W in harbour, 25 W at sea and always in distress.
The certificated operator is in charge of the set; crew use it under supervision, and anyone may call in distress. Coast stations announce weather on 16 and read it on a working channel. The handheld, for dinghy and liferaft, needs its charger.
DSC needs the boat's MMSI programmed and the cover on the red button. When an alert comes in, listen on 16 and note the position: the coast station answers; you call only if nobody does and you can help.
Ch 16False DSC alert sent
Stop it on the set
Then by voice on channel 16: ALL STATIONS × 3 this is (name, call sign, MMSI) position
CANCEL MY DISTRESS ALERT · OUT
7 · Lights and horn
Which switches go on, and when
What lights does a sailing yacht show at night when motor-sailing?
Navigation lights plus the steaming light: with the engine driving you are a power-driven vessel, sails up or not. Under sail alone show the tricolour or the deck-level lights, never both.
Engine onNAV + STEAMING
Sail aloneTRICOLOUR, or NAV
At anchorANCHOR only
With the engine driving you are a power-driven vessel, sails up or not. Under sail alone show the tricolour or the deck-level lights, never both. At anchor show the all-round white only: sidelights mean under way. Deck light off: it blinds the helm. A vessel of 12 m or more carries a whistle: the electric horn, with the aerosol can as the spare. Test both.
Practice questions
Questions from this topic, as the app asks them. Open one to see the answer.
Chartplotter
Power on · fix: 9 satellites
Chart card: Greece — Ionian
Edition date: not shown
Position: the berth
The technician switches on the chartplotter, waits for the fix, shows you this and turns to the VHF. What do you ask before he moves on?
Whether the card covers the whole cruising ground, and how old the chart is
Whether the plotter also drives the autopilot
Nothing — a plotter with a fix is a working plotter
Whether the screen can be dimmed for night passages
Show the answer
A. Whether the card covers the whole cruising ground, and how old the chart is
Check the chart covers everywhere you will go and ask its edition: an old card misses new marinas, moles and shoals.
All 50 questions of this topic are in the app: practice by topic with the reason after every answer, your mistakes brought back, and a timed mock exam. Free, no sign-up, in the browser or in Telegram.
