Mercury outboards...Choosing your engine

There are a number of points to take into consideration when selecting the correct outboard engine for your boat.

Where will your outboard be used?

The first thing to consider when choosing outboard engines is where is the outboard mainly being used. Running offshore and in coastal waters will have different requirements than on rivers, canals and lakes. For example lake trolling would call for smooth and quiet operation whilst going offshore would call for speed, acceleration and top-end performance.

4-Stroke or 2-Stroke?

Mercury petrol outboards are available as 4-stroke, 4-stroke Verado, 2-stroke (see new 2007 2-stroke regulations) and Direct Injection OptiMax 2-stroke. All 4-stroke Verado and OptiMax engines are designed to meet the stringent emission standard (EPA 2006).

Mercury 4-stroke outboard engines are available with either electronic fuel injection (EFI) or naturally aspirated (with a carburettor). Listed below are the features and benefits for each engine type:

Mercury Four-Strokes

Inherent four stroke characteristics include quiet, smooth operation and exceptional idling

Superior corrosion protection provides longer life

Precision engineered shift system for an improved driving experience

Consistent, easy starting

Outstanding fuel efficient economy

Clean running engines for ultra low emissions

Optional SmartCraft technology monitors boat and engine functions (40hp to 115hp engines only)

2 year limited warranty for leisure use only

Mercury Verados

The first ever supercharged four stroke delivers best-in-class torque and acceleration

Mercury Verado outboards are the most proven marine power ever produced with more than 25,000 hours of testing

All major structural components specifically designed and built for maximum performance and reliability

SmartCraft digital throttle and shift provide smooth, quiet shift engagement and instantaneous throttle response

SmartCraft technology with the Engine Guardian System monitors engine functions

An insulated cowl system reduces engine noise plus patented induction muffling chambers and idler relief silencer

Dramatically better torque than any four stroke and most two strokes

3 year limited warranty for leisure use only

Mercury OptiMax outboards

Outstanding fuel economy

Powerful and lightweight for outstanding acceleration and top speed

3 year limited warranty for leisure use only

SmartCraft technology - monitors everything from fuel flow to GPS

Exclusive Engine Guardian System constantly monitors over 40 sensors to give you advance warning of possible problems and takes action to minimise their potential impact

Powerful, reliable 60 amp alternator system charge

Exclusive XK360 aluminium alloy providing excellent protection against corrosion

No engine oil and oil filter changes required

Two stage direct fuel injection technology, smooth, smoke free, durable and reliable

Built-in fresh water flushing system

Calculating shaft length of engine

Petrol outboards are mounted onto the transom (stern) of the boat. To determine the correct mounting height you need to measure from the bottom of the boat to the top of the transom to find the correct shaft length.

Calculating Weight and Horsepower

Information relating to weight and horsepower can be found on the hull number plate which is fitted on the boat. Here you will find the maximum kW/hp/weight recommended for an outboard engine. The manufacturers recommended horsepower rating should not be exceeded. Older boats may only have information regarding maximum horsepower rating and in this case it would be advisable to contact the boat builder for maximum weight.

Propeller Selection

In determining boat performance, boat propellers are second in importance only to the power available from the engine. The boat's propeller affects every phase of performance, handling, riding, comfort, speed, acceleration, engine life, fuel economy and safety.

The boat propeller is the primary connection between the engine and the water. Which propeller or propellers you select to make that connection is critical to achieving optimum boat performance. Every engine will produce its maximum horsepower at the maximum wide open throttle rpm which is stated for every engine.

(This can be found in the Owners Handbook). For every one pitch you change the propeller the wide open throttle will change approximately 250rpm. If the engine is over propped the engine will not reach maximum rpm.

This will result in high fuel consumption, loss of power and potential engine damage. If the engine is under propped this will allow the engine to over rev resulting in high fuel consumption and potential engine damage.