Engine Choices
Unfortunately there is no such thing as a purpose designed hovercraft engine. The engines in use today are derived from many sectors such as the industrial, automotive, aviation and motorcycle areas.
The most important thing is weight. This cannot be over-emphasised, no amount of power will make up for the extra weight of some enormous automotive V6. The performance of a craft fitted with a small 25hp garden tractor engine can be better, size for size, than the same craft fitted with a 100hp car engine.
2 strokes
2 strokes have favourable weight – they are incredibly light. But, for cruisers today, the disadvantages of poor reliability, high fuel consumption and high noise levels outweigh the weight advantage. There are some reliable 2 strokes, such as the Rotax microlight engine, but they still have very poor fuel consumption – a typical 50hp 500cc twin can consume 5 gallons an hour.
Many would agree that two strokes are best avoided for cruising use.
4 stokes
4 strokes are heavier than the 2 stroke alternative, but are quieter and more efficient, and generally more reliable.
A few lightweight car engines and some motorcycle (not high revving) engines are suitable. Look for all- aluminium engines.
Recent developments in 4 stroke microlight engines are very suitable for hovercraft, but may be a little expensive.
Diesels
Whilst many agree that diesel reliability would be an advantage, they remain heavy just at present so there are few small diesel powered craft around. There are a number of developments in lightweight diesel engines, so this may change in the future
Small craft
The Briggs and Stratton, Kohler or similar industrial/garden tractor engines are suitable for small craft, say between 10 and 14 feet. Car engines are likely to be too heavy for this size of craft.
Larger craft
Craft of 14 feet and upwards may be suited to the lightweight car engines, such as the Subaru flat fours, or Suzuki 3 cylinder engines.