The height of outboards in relationship with the bottom of the hull is very important. The higher or “drier” the motor is the faster the boat will go until it reaches the point of ventilation “pulling air into the propeller” which will instantly slow you down. Most motors will be set a little bit lower to take off best. The motor can be trimmed, meaning hydraulics will rotate the engine higher at an angle, this will speed you at higher speeds. This works unless the boat front starts to bounce or “porpose” then the motor trim will need to come back down a little bit. Idealy the motor will have a jacking plate that moves the engine straight up and down instead of on a pivot like the trim. The propeller is very important and has to match the motor and boat to obtain the best performance. A prop that limits the motor speed to max rpm at wide open throttle is ideal. Some people use different pitch props to gain acceleration or top speed. Two numbers describe prop pitch the first number tells the diameter of the prop and the second tells the pitch.
Two and four stroke outboards are more similar in terms of performance and efficiency than ever before. Four strokes have become far more lightweight with more power than before. Two strokes have become far more fuel efficient while keeping their excellent power to weight ratio. Some companies such as mercury marine have produced four stroke engines with supercharging and intercooling to increase power with minimal increase in weight. Many other companies such as johnson stand firm in the belief that two strokes are still the best engine configuration to use. Most companies still offer two strokes while newer models are four stroke. All outboard companies accept the fact that the four strokes weigh slightly more. Most consumers don’t seem to mind having a little extra weight for four stroke technology that is far more common in today’s engines. Unfortunately with lightweight four stroke technology comes a hefty price tag also. People that have businesses of chartering fishing trips or that log high amounts of hours on their engines may see an advantage using a slightly more fuel efficient motor. Most boaters will never see enough of an advantage to regain the cost difference of a four stroke engine or possibly even a direct injection two stroke. The alternative being fuel injected two strokes or possibly old model carbureted engines, which are considerably cheaper initially and possibly overall.
The basic outboard marine boat motor is of two stroke design. This is due to the weight of the motor being less. The power of a two stroke motor is also higher versus a comparable weight four stroke motor. As emissions became tighter direct injection two stroke engines have been produced. They still have low weight and alot of power but are very complex. Direct injection two stroke outboards are actually very clean motors and get excellent fuel economy similar to four strokes. As the technology of four strokes evolve, they have become much lighter and have flooded their way into the market. Although pricy four strokes are very popular and are getting closer to the weight and power of two strokes. Outboard motors started as two strokes with lower weight found on much smaller boats than boats produced today. Today it is not uncommon to see a 250 horsepower motor on the back of a bass boat! Many offshore boats may have twin 250 hp or 225 hp outboard motors on the back! Most mid sized ski boats generally use 115 or 150 horsepower outboards. Small john boats generally use 5,15 or 25 hp motors. Small skiffs use anything between 25, 40 and up to 115 hp outboards.