Check the board before the session: buying a used electric boat

Picture the listing. Lovely little electric launch, one careful owner, quiet as a library, half the price of new. The photos are glassy and the seller is keen.

Before you fall for it, remember what you are actually buying. On a used electric boat, the hull and the motor are usually the easy part. The battery is the expensive, ageing heart of the thing, and it does not show its condition in a photo.

We pulled together what makers, insurers and safety bodies say, so you know what to ask before you pay.

The battery: the set wave of every used deal

Start here, every time. Ask the seller for:

• Age and original capacity. When was it bought, and what size was it new?
• Remaining capacity. Many systems log this in the battery management system. A dealer can often read it out.
• Storage history. How was it kept over winter, and at what charge?
• Deep discharges. Has it ever been run completely flat?

That last one matters. ePropulsion's guidance for its Spirit battery says that if it fully discharges to 0 percent, it cannot be recovered and must be replaced (Oceans EV). A battery left flat over a long flat spell can be a very expensive surprise.

A sea trial helps. Run at a steady cruising speed for a set time and compare the drop in charge with what the maker's range figures suggest. A battery that empties far faster than it should is telling you something.

Warranty: read the small print before you head out

Battery warranties vary by maker and by years, cycles or remaining capacity. Find out:

• How long the battery warranty runs and what it covers.
• Whether it transfers to a second owner.
• Whether it depends on servicing at a dealer.

Ask the manufacturer or dealer directly, with the battery serial number, and get the answer in writing. A seller's "it's still under warranty" is a start, not a guarantee.

Installation: who wired the quiver?

Factory-built electric boats and dealer-fitted systems are the safest bet. Home conversions need a closer look.

The Boat Safety Scheme says installed lithium battery systems should be fitted by competent persons to suitable industry standards, using batteries and components intended for marine use, and that different battery chemistries should not be connected in parallel or in series (BSS).

Things to look for:

• Batteries and charger from a marine supplier, matched to each other.
• Tidy, protected wiring, fuses and an isolation switch.
• No mix of battery types in one bank.
• Documentation from whoever did the work.

If the seller cannot say who installed it, treat that as a warning sign.

Insurance: check before you drop in

Get an insurance quote before you buy, not after. Lithium systems can make cover harder to find.

Pantaenius says insurers prefer modifications to be done by professionals and that a well-documented maintenance history helps a boat's insurability (Pantaenius). One owner of a DIY electric conversion found that several insurers wanted a surveyor's report, and that lithium batteries fitted by amateurs needed a review by a qualified professional (Practical Boat Owner).

Our guide to insuring an electric boat covers this in more detail.

Charger, cables and the boring bits

The charger is easy to forget and expensive to replace. Make sure the original charger and cables come with the boat, that the plug suits the marinas you will use, and that any shore power inlet is in good condition.

Then the usual boat checks still apply: hull, steering, controls, trailer and paperwork. Electric changes the engine room, not the rest of the boat.

Our verdict: buy the battery, get the boat

So, is a used electric boat a good buy? It can be a great one. Fewer moving parts means less to wear out than on a petrol boat.

But judge the deal on the battery. A healthy battery with a clear history and a transferable warranty makes a used boat a bargain. A tired battery with no paperwork turns it into a project.

Before you commit, read electric boat battery care and electric boating explained.