How to Buy a Boat Engine or Motor: Comparison Tools

Boat Engine

Choosing the right type of engine or motor for your boat is a very important matter. Its weight and horsepower will both have an impact on the performance of your boat. If your vessel is underpowered, its engine will work hard continually and will provide poor performance. Additionally if your boat is overpowered, it may exceed the safe operating speed that was designed for the vessel.

Size Matters

When you're choosing the appropriate power for your boat, consider the size and weight of the boat and remember that weight includes your passengers, fuel and gear.

A good rule is to come as close as possible to the maximum horsepower that your boat is rated for.

Both weight and horsepower will have an impact on the performance of your boat. If your vessel is underpowered, your engine will work harder than it needs to, possibly leading to more routine maintenance.  The boat will also not perform to your expectations which may leave you unhappy with the boat.  This may also lead to higher fuel consumption. 

Additionally, if your vessel is overpowered, it may exceed the safe operating speed that was designed for the vessel. Manufacturers and dealers will all have a recommended power package for each and every boat that they manufacture and sell. 

Pick Your Power

When looking at gasoline engines (outboard, stern drive or inboard), there are three distinct types of fuel delivery systems on the market.  They are: Direct Fuel Injection (DFI), Electronic Fuel Injection (EFI) and Carbureted. 

Each fuel delivery system is unique in its own way and there are benefits to each system.


Direct-Fuel-Injection (DFI)

In a direct fuel injection system, the fuel is directly injected into the engine's cylinders.  This helps control and raise fuel economy and compression ratios in relation to the engine's overall performance.  High pressure fuel pumps and fuel injectors are a couple of the key components when looking at the system.

Benefits

  • Low emissions
  • Excellent fuel economy
  • Instant turn key starting
  • Smooth idling
  • Reduced vapor lock in warmer climates
  • Ability to automatically adjust to altitude, air and water temperatures
  • Superior throttle response and power
  • Availability of self diagnosis systems
  • Sealed fuel system (helps to eliminate fuel oxidation)

Electronic Fuel Injection (EFI)

Electronic Fuel Injection functions on three basic systems; fuel delivery system, air induction system, and the electronic control system.

The fuel delivery system maintains a constant pressure through the use of an electronic fuel pump.  The air delivery system controls the amount of air needed to burn the fuel efficiently.  Finally, the electronic control system or some times called the ECU unit controls the fuel injectors and determines how much fuel and air needs to be delivered into cylinders at any given time.  

Benefits

  • Uniform air and fuel distribution
  • Superior throttle response and power
  • Usually excellent fuel economy
  • Cold engine start ability
  • Availability of self diagnosing systems
  • Low emissions (especially 4-stroke)

Carbureted Fuel Systems

Carbureted engines have been around for several decades now.  When looking at a carbureted engine, you will notice the carburetor on top of the engine.  The carburetor controls the amount of air flow and fuel into the engine.  This is a mechanical process that is controlled by a throttle body cable that is usually hooked to the throttle at the helm.  Again, this is an all mechanical process.

Benefits / notes

  • Lowest initial cost
  • Simple by design
  • Higher emissions than an EFI or DFI system
  • Poor fuel economy when compared to an EFI or DFI system