Chartplotter Archaeology: Working Out What a Used Boat's Dash Is Really Worth

There's a moment in most viewings when the owner taps a screen proudly and says something like "all the electronics were done a few years back." It's rarely a lie. It's just that "a few years" in marine electronics can mean anything from last season to the tail end of the Blair era, and the difference between those two is a four-figure sum you'll be the one paying.

Hulls age slowly and honestly. Gelcoat fades, teak greys, a surveyor can thump a stringer and give you a view. Screens do the opposite — they look fine right up until the moment you need a chart update, a spare transducer or a warranty, and then the whole system quietly tells you it belongs in a museum.

So before you get sentimental about the joinery, do a lap of the helm with a notebook.

Start with the model, not the brand

Most UK boats carry Raymarine, Garmin, B&G, Simrad or Lowrance at the helm, with a fair chance of a mixed bag below. Brand tells you almost nothing. Model tells you everything.

Raymarine's path is a decent worked example. The old C and E series were solid kit in their day and are now firmly in the "works until it doesn't" bracket — parts dry up, software updates have stopped, and the chart cards they take aren't the ones the chandlery stocks any more. The later eS and Axiom ranges are a different world: still supported, still getting updates, still saleable secondhand.

Garmin rewards a bit of homework too. GPSMAP units from the 700, 800 and 1000 families are old soldiers, while the newer x3 generation is current, supported and — importantly — still has a healthy resale market. B&G's Zeus range has similar fault lines: Zeus and Zeus2 versus Zeus3 and Zeus3S. Simrad's NSS sits in the same pattern.

You don't need to memorise the whole catalogue. You need to photograph the model badge on every screen, then spend twenty minutes online when you get home. If the manufacturer's own support page lists your unit under a discontinued heading, that's your answer.

Age the system by its plumbing

The screen is the easy bit. What sits behind it decides whether a modest upgrade is possible or whether you're rewiring the boat.

Look for the network. A boat running NMEA 2000 — the modern backbone standard, usually a fat cable with T-pieces and terminating resistors — is a boat you can add to. A boat still running a spider's web of NMEA 0183 serial connections, or Raymarine's older SeaTalk, can still be lovely, but every addition means converters, adapters and somebody's hourly rate.

Ask about the chart format as well. If the plotter takes the current card or download subscription from Navionics or C-MAP, fine. If it needs a proprietary cartridge that no longer exists in the size you need, you've effectively bought a fishfinder with a map printed on the outside.

Radar deserves its own line in the notebook. Old magnetron domes work, but magnetrons have a service life and replacement parts get scarce. Solid-state sets — Raymarine Quantum, Simrad HALO, Garmin Fantom — are the modern default and also tell you roughly when the installation happened.

Autopilot is the sleeper. A working unit with an Evolution or similarly current brain and a serviceable drive is worth real money. A 1990s wheel pilot with a cracked belt and a control head held together with hope is not an autopilot, it's a project with a tiller-shaped hole in the budget.

The tell-tales that say 'walk away'

Some of this is just looking properly.

• Screens with visible delamination, cloudy patches or dead pixels. That's the beginning of the end, not a cosmetic gripe.
• Touchscreens that need a firm press in one corner. The digitiser is going.
• An AIS that only receives. Fine for seeing others, useless for being seen, and a transponder swap means more than a plug.
• Any unit whose manufacturer no longer publishes firmware for it, or whose app has vanished from the stores.
• A dash where the cabling disappears into a void with no fuses, no labelled breakers and no diagram. That's not electronics, that's archaeology.

Put a number on it, then put it on the table

This is where the work pays you back. Before you make an offer, price the realistic replacement of anything tired. Rough 2026 figures for supply, before fitting: a decent nine-inch multi-function display lands somewhere around £1,500 to £2,500, radar a couple of grand and up, an AIS transponder £600 to £1,200, an autopilot system £1,500 to £3,000 depending on the drive. Add marine labour at £70 to £110 an hour, plus a haul-out if a transducer or through-hull needs swapping.

Now be honest about what you'd actually do in year one. If the plotter is old but the charts are current and you sail the same estuary every weekend, you may not care. If you're planning a first Channel crossing or a season on the west coast of Scotland, you will.

How it changes the conversation

Don't arrive with a list of grievances and no evidence. Arrive with photographs of the model badges, a printed spec sheet showing the unit is discontinued, and a chandler's quote for the replacement you'd actually fit.

Then frame it plainly: "The hull and engine are priced fairly. The electronics need about £4,000 to bring up to standard, so I'd like to talk about the price in light of that." Owners respond far better to a quote than to a sniff.

It also gives you two ways to settle. A price reduction lets you buy the kit you want in your own time. A seller-funded upgrade before completion sounds tidy and rarely is — you inherit their choice of model, their installer and their timeline.

One last thing worth saying. Electronics depreciate hard and fast, which is exactly why they're a buyer's opportunity. A boat with tired screens and a good hull, a strong engine and a sound rig is often the best-value thing on the pontoon. You're not looking for the newest dash. You're looking for one where you know, to the pound, what the old one will cost you — before you sign anything.