2 Stroke vs 4 Stroke Outboard Motors: A Side by Side Comparison

October 18th, 2019 by

More Canadians than ever are enjoying life on the water. The sale of outboard engines is 20% higher than they were in 2010. These engines are also getting more powerful.

Today the average is 58 horsepower. While in 2010, the average engine power was 46 horsepower. Another development is the increase in the debate of 2 stroke vs 4 stroke.

Most people shopping for a new motor assume that a 4 stroke is more powerful and, therefore, better. This isn’t necessarily the case.

We are going to explain the differences and how you can decide which one is right for your boat.

 

How These Engines Are Similar

Both of these engines have a piston that is located inside of a cylinder. Air and fuel will enter the cylinder, and the piston will move to compress this mixture.

When fully compressed, the spark plug will fire and create a mini-explosion. This will force the piston downward in the cylinder. This movement is what causes the crankshaft to move and transfer the power from energy to physical action.

There are five functions to the entire combustion cycle: intake, compression, ignition, combustion, and exhaust.

 

Two-Stroke Outboard Motors

In a two-stroke motor, these five stages occur in two strokes of the piston. The crankshaft will turn once for every cycle of the piston. This engine creates power once every two strokes of the piston.

There is a single chamber that has two ports connected to it. One port allows for the entrance of air and fuel. The other allows for the exhaust gas to be expelled. This is a relatively simple design.

You will also notice that the piston isn’t flat on the top. The pistons in these motors tend to have a bump or dome shape to the top of them.

 

Modern Advancements

The two-stroke motors that are on the market today are not the same engines of old. Today there are direct fuel injection (DFI) and Electronic fuel injection (EFI) models.

Traditional two-stroke engines were carbureted. These engines lag when it comes to fuel economy and emissions standards.

DFI outboards have the fuel directly injected into the cylinder. This is different from the carbureted design that depends on the air to carry the fuel into the cylinder.

An EFI outboard will use a small computer or electronic system to control the flow of air and fuel. This will exert greater control over the system and therefore increase fuel economy and comply with modern emissions standards.

 

Advantages

These motors tend to be smaller and lighter. This makes them perfect for use in smaller applications. Thanks to their simpler design, they cost less to manufacture and repair.

 

Disadvantages

Users will notice that these motors are louder. You will also need to maintain a consistent maintenance schedule, or these engines will end up requiring repairs more often than their four-stroke counterparts. Be sure to add oil regularly to save money in the long run.

Older two-stroke engines are not as fuel-efficient or environmentally friendly as modern engines.

 

Four-Stroke Outboard Motors

In a four-stroke engine, the five combustion cycle steps occur in four strokes of the piston. The crankshaft makes two rotations for every one cycle of the piston. This means that power is created one time for every four strokes.

Instead of having two ports that get covered and uncovered, a four-stroke motor uses valves. This is a slightly more complicated design and requires gear and chain mechanisms for it to function.

The pistons in these motors tend to be flat across the top.

 

Advantages

If noise is an issue for you, then these engines are the quieter option. These engines don’t require you to add oil, are more fuel-efficient, and have greater durability.

 

Disadvantages

One significant disadvantage is that these engines tend to be heavier. They also require regular maintenance checks that are best done by a professional service team.

 

Choosing the Right Outboard Engine for Your Boat

The traditional go-to engine for boats were two-stroke engines. Their zippy throttle response and lightweight makes them perfect for use on the water. However, four-stroke engines have gained a following thanks to their more refined performance and cleaner operation.

Think about the size of your boat and how you intend to use it. Take a fishing enthusiast as an example.

 

Intended Use

Someone who is a tournament angler will do well with two-stroke motors. They will get the boat up on plane fast to get the fisherman to the prime spots.

But if the fisherman prefers to idle along and look for bass, then a four-stroke motor might be a better fit. It will stay quiet, so the fish are less likely to spook. Plus, it gets better fuel economy and will maintain that steady slow speed better and for longer.

 

Type of Boat

Another consideration is the type of boat you intend to put the engine on. All boats have a plaque indicating their maximum weight capacity. If you have a smaller boat, it may not be able to withstand the weight of a four-stroke engine.

Bigger boats or those designed to carry heavy weights have hulls that can handle the increased torque that a four-stroke engine will produce.

Ignore this weight restriction, and your outboard motor will put undue stress on your hull. This will cause cracking, leaking, and breaking.

 

2 Stroke vs 4 Stroke, What’s Your Choice?

When it comes to the 2 stroke vs 4 stroke debate, it is more than just which one is more powerful. Thanks to technological advancements, two-stroke motors have quickly caught up to their four-stroke counterparts in terms of fuel efficiency and environmentally friendly operation.

Focus your decision on your intended use, type of boat, budget, and maintenance requirements. This will ensure you have a motor that will perform the way you need.

Whether you are looking for a two or four-stroke motor for your boat, browse our extensive inventory to find just what you need.