Buying an outboard engine for your boat is no walk in the park. There are a whole host of important factors to consider, and one of the most significant decisions is whether to pick up a two-stroke engine or a four-stroke engine.
These two types of outboard engine are based around the same principles of internal combustion, but they are engineered to perform very differently. Essentially, a two-stroke engine uses an intake and an exhaust stroke, so all air, fuel and combustion materials are moved during those two strokes. In a four-stroke engine, a separate stroke is used for moving burned and unburned mixtures. There is a stroke for intake, compression, expansion and exhaust.
It might seem like a small difference, but it makes an impact, and most people will find themselves better off with a four-stroke outboard.
Here are just three important reasons to choose a four-stroke outboard motor.
1. Enhanced Efficiency
Each cylinder of a four-stroke outboard is held shut by springs, only to be opened by a crankshaft driven camshaft at the appropriate time. As such, fuel that has not yet been combusted is not allowed to escape through the exhaust chamber. Additionally, four-stroke engines consume fuel every four-strokes instead of every two-stokes. You don't need to understand all this – the take-home message is that four-stroke outboards use their fuel more effectively, so you can expect them to output fewer emissions and run far more efficiently.
2. Improved Durability
A two-stroke engine needs to use air or fuel to carry oil to critical components, while a four-stroke covers each internal component with oil to ensure constant lubrication and cooler operating temperatures. A two-stroke engine also runs a lot faster than a four-stroke, and intake and exhaust ports can accelerate wear. These issues all contribute to one important point: a two-stroke engine will generally be less reliable and suffer from reduced durability compared to a four-stroke engine.
3. Reduced Oil Consumption
It isn't just fuel that two-stroke engines consume more readily than four-stroke engines. Because they require oil to be mixed in with the air-fuel mixture, oil tends to run out quite quickly. With a four-stroke engine, you're still going to need to add oil to the moving parts occasionally, but no extra oil is going to be required for the fuel. Additionally, two-stroke engines tend to generate more pollution because the oil in the air-fuel mixture can combust and produce smoke.