how the efficiency of boat engines can be increased?

Question

which fuel should be used...what type of engine must be used...what precautions should be taken.......so please help me

Answer 1

This may be hard to answer.
IF, you talking Fuel Burners then efficiency most likely be increased by Hull Design.
For example. park your car on level ground and keep someone at the wheel. With the car in Park, try pushing it. If you had the Strength soon the tires would start sliding. But, it require a lot of energy to do this. Now put the car in Neutral and try pushing. It will most likely start to roll with not much effort.
OK, boat are similar to the car example. If, there is a lot of water resistance to the hull (Car in park) it going to take more effort on the engine to make it move. Less resistance on the hull (Car in neutral) the engine work less to move the boat. Thus it more efficient.
The type of propeller can help. Gas "may" (I said may, lol) be more efficient than Diesel but it more flammable.
Electric is an alternative that we may see more of. Locomotives (Trains) are "not" driven/pulled by those diesel engines. The diesel engines run the generators to run the electric motors that move the wheels. So, it may be possible to one day use Electric motors to move a boat and the engine just run the generator or charge the batteries.
And we already see this to some extent. Trolling Motors and on some Sailboats is an electric auxiliary motor in place of a fuel burner.

Answer 2

Slow down mid range fuel>

Answer 3

Once you get your boat on plane back off the throttle till it just falls off plane and increase it till it just gets back on plane. That is the point of maximum efficency
Basically what 45 cal said

Answer 4

the question is to vague, are you talking about inboards, outboards, racing, fishing or towing a skier...every engine has factory recomendations for fuel, mixing, performance etc. read the manual.