What is the typical fuel consumption of a boat?

This is a very difficult question to answer as a great variety of engines are used and average consumption therefore varies, especially at river cruising speed. A small outboard, particularly modern 4 strokes, at a river speed of around 5mph will often take longer than 2½ hours to consume a gallon (5 litres) of petrol. A craft with larger twin petrol engines might only run for half an hour on a gallon of petrol with both engines running. There is of course a difference in running costs between petrol and diesel. Petrol is much the same as regular pump prices but diesel is sold at 3 rates of duty. The first is completely duty free, this is for dispensing into cans for heating or agricultural use only. The second is for boats with a heating system on board and this is priced with a duty split of 60% with duty (used for propulsion) and 40% which is duty free (used for domestic use). This is based on a government estimate of what typical pleasure craft use might be as fuel used for propulsion became a taxable commodity in 2008. The third is for craft with no heating and the full levy applies. As a guide the three prices for diesel varies from about 75 pence per litre to about £1.30 per litre. Most craft on rivers run between 50 and 100 litres per year though this can vary. Please note if a sports cruiser is used at sea fuel consumption will significantly increase.