Impalas are about the biggest boat you can tow with a normal driving licence

A great advantage of the Impala is that it will fit on a road trailer -meaning you can trail it to events, cruising grounds, and lay up for the winter and avoid boatyard charges. But it’s just about the biggest boat you can tow with a large 4×4 before you get into special loads territory.

‘A loaded trailer can double your overall weight, meaning slower acceleration, reduced hill-climbing ability, lower overall speed, greater fuel consumption and significantly longer braking distances’, warns the Highways Agency. It’s not surprising, then, that many drivers and boat owners approach the subject of towing a trailer with some trepidation.

Before you hit the road, be warned – there’s a  minefield of confusing information and misleading advice out there. Contravening the regulations can invalidate your insurance and vehicle warranty, as well as increasing wear-and-tear, so it’s worth reading on to make sure you won’t be doing something illegal.

Jargon buster:

Kerb Weight: Sometimes called the Unladen Weight, this is the weight of the empty vehicle. Check your owner’s manual. Different from EC Kerb Weight, which includes a notional weight for the driver.

MAM (Maximum Authorised Mass): This is your vehicle’s maximum permissible weight, also known as the Gross Vehicle Weight.

Maximum Combination Weight: The total permissible weight of the fully-laden tow car and trailer combined. Also known as Gross Train Weight.

Noseweight: The weight pushing down on the towbar. There will be a maximum quoted in your owner’s manual. An easy way to check light noseweights is using bathroom scales and some blocks of wood – or head to a nearby weighbridge.

Payload: The weight your vehicle can carry, calculated by taking the difference between MAM and the kerb weight.


Before we look into whether your car can legally tow your boat, lets see if you are you licensed to drive it. If you passed your driving test before 1st January 1997, you’re probably OK. Check your driving licence – it’s likely that you’re entitled to drive up to a category C1+E – a vehicle and trailer combination of up to 8.25 tonnes MAM. Remember that it doesn’t matter what’s on the trailer – it’s the MAM that counts.

Category B

If, however, you passed your test on or after 1st January 1997, the weight you may tow is much lower. You can drive a Category B vehicle (with a MAM of 3,500kg), and a trailer with a MAM of up to 750kgs, provided the combined MAM does not exceed 4.25 tonnes. You may also tow a trailer with a MAM over 750kgs, as long as the MAM does not exceed the kerb weight of the towing vehicle and the combined MAM does not exceed 3.5 tonnes.

Anything over 3.5 tonnes MCW/GTW and you’ll need to take a practical test in order to upgrade your licence to Category B+E, which covers vehicles up to 3.5 tonnes MAM and trailers with a MAM of 750kg and above, providing the combination does not exceed 8.25 tonnes.

Driving Licence Categories:

B: Vehicle up to 3.5 tonnes MAM and eight passenger seats

C1: Goods vehicle 3.5 to 7.5 tonnes MAM

E: Entitlement to tow trailers

Trailer Categories:

01: Trailer up to 750kg MAM. Does not require brakes.

02: Trailer of 750kg to 3500kg MAM. Must be braked.


Trailers with a MAM of more than 750kg must be braked. In addition, you cannot use an unbraked trailer which exceeds 50% of the kerb weight of the towing vehicle.  For trailers up to 1500kg laden you can use secondary coupling, usually a wire strop that hooks over the tow hitch, which in the event of separation  will keep the trailer attached to the towing vehicle, prevent the nose of the trailer from touching the ground and provide some residual steering of the trailer. Trailers over 1500 kg MAM trailer must be fitted with a device to stop the trailer automatically in the event of separation – this is normally achieved by a breakaway cable, which will apply the brakes if the trailer becomes detached from the towing vehicle.


It goes without saying that the lightboard should be in working order and with a matching numberplate to the towing vehicle. It should be no more than 1.5m from the ground or 2.1m if the structure of the vehicle makes it impracticable. Indicators must flash in unison with those of the towcar and a dashboard warning light or buzzer must be fitted.

Preparing to tow

Before you go anywhere, give your car and trailer good once-over.

Check tyre pressures of the car and trailer, and make sure you’ve got a correctly-inflated spare for both, too.

Your engine will be working hard, so check the oil and coolant levels.

Check the trailer coupling – it should be securely attached to your car, and a safety strop or breakaway cable, if fitted, should be securely attached to the vehicle.

Make sure the boat is well tied on, such that it can’t move side-to-side, forwards or backwards, and that any knots or ratchet straps are tight and there’s no loose ends trailing or flying in the wind.

‘In particular, check brake cables and linkages, if fitted – these can seize up, lead to overheating and ultimately, the wheel coming away from the trailer’ warns Inspector E Henley of Dorset Police’s Traffic Unit. ‘Finally, make sure any sharp or dangerous projections – like propellers and masts – are protected by buckets or reinforced, orange bags.’

Check your lights work and that the lightboard is securely attached.

Finally, before you leave, ensure your jockey wheel is clamped in its ‘up’ position, and the trailer’s handbrake is released.

How to tow on the road

That’s the small print out of the way, now down to the basics of towing. There’s no great secret to driving with a trailer – you just need to take care and make sure you think ahead.  Bear in mind that you’re limited to 50 on single carriageway, and 60 on dual carriageways and motorways. When towing a trailer you cannot use the outside lane when there are three or more lanes. You also cannot park a trailer without lights on a public road at night, whether or not it’s attached to a vehicle.

Driving tips:

Anticipate stops, brake early. Your combined car and trailer will weigh far more than you’re used to – so stick to a reasonable speed and brake early. Always brake in a straight line for maximum safety and control. It’s a good idea to leave a 4-second gap between you and the car in front.

Take care at corners. With a now longer vehicle, you’ll need to take a wide swing as you go round corners and roundabouts so your trailer doesn’t clip the curb. The same applies if you’re overtaking another car or obstruction.

Long climbs… Your engine will be working harder than usual, and on long climbs can be susceptible to overheating. Be aware of this, and be prepared to stop if necessary. Generally, lower gears will keep your engine running cooler.

…and drops: use your engine as a brake by selecting a low gear when going downhill.

Motorway Driving: It’s worth making sure your breakdown cover will cover trailer recovery. You’re limited to a maximum speed of 60mph and cannot use the outside lane – so accept that your journey will take longer and be more tiring – and plan accordingly.

Stop frequently: A few minutes’ rest will help you get to your destination in one piece – and let you check the trailer. Check your boat is still tied on properly, and feel your wheel hubs to make sure they’re not too hot. If it’s been raining, ensure your boat isn’t dangerously heavy and full of water.

Dealing with snaking. Horror stories abound about the dangers of snaking, where the trailer takes control. If it does happen to you, ease off the accelerator and keep steering straight – but don’t, whatever you do, hit the brakes or try to correct it by steering. Snaking is down to a poorly balanced load, with the centre of gravity too far back, which causes the trailer to yaw. This is a common problem for boats on trailers, many of which have heavy engines on their transoms. Moving the centre of gravity forward will help. Too far forward and you risk exceeding the figure quoted by the vehicle manufacturer – but by and large you want the trailer’s centre of gravity to be 10-20cm forward of its wheels.