Walking through the boat dealership is an exciting experience. From bay boats to bowriders, cabin cruisers, and yachts, dozens of boat models are available to suit any pastime out on the water, from fishing to watersports.
While most of us focus on the boat we like, few new owners take the same amount of time selecting the right motor for their vessel. The outboard engine is the most common propulsion system for smaller watercraft up to 40-feet.
The outboard sits outside of the boat, hanging from the transom, which is the cross-section at the vessel’s stern. Outboard motors are available for leading manufacturing brands like Honda, Yamaha, and others. They come in various capacities to suit the size of your boat and your activities out on the water.
Choosing the right outboard motor for your boat is essential to getting the most value from your boating experience.
If you choose a low-powered motor, you’re not going to have the performance you need for watersports of navigating rough waters. Too high a capacity means that your boat won’t be able to enjoy the full operating potential of the engine.
We decided to put together this post to give you everything you need to know about choosing the right outboard motor for your boat.
- Two-Stroke or Four-Stroke – Which Is the Better Choice?
- Buying Your Outboard Motor – New or Used?
- Calculating Outboard Motor Capacity for Your Boat
- Why Should I Choose a Larger Outboard Engine?
- What are the Top Features to Look for In an Outboard Motor?
- Is A Dual Outboard Setup the Best Choice?
- Do I Need High-Octane Fuel for the Outboard Motor?
- How Do I Select the Right Propeller for My Outboard?
- Propeller Basics
- What to Know About Boat Engine Propellers
- Easy Outboard Engine Maintenance Tips
Two-Stroke or Four-Stroke – Which Is the Better Choice?
Outboard motors are available in two-stroke and four-stroke models. The industry seems to agree that the four-stroke motor is the better choice for any boat. However, if we dig into the tech behind these engine configurations, the consensus seems to disappear, and there are several advantages to fitting your vessel with a two-stroke motor.
With a four-stroke motor, you’re getting a similar design to what you expect in a car engine. The engines operate on gasoline, with oil circulating through the system to lubricate the working parts motor.
Two-stroke motors operate on a blend of gasoline and oil, feeding the oil/gas fuel mixture through the carburetor or injectors into the cylinders through intake valves. Carb-based models are somewhat inefficient, and up to 30% of the fuel and oil mix entering the engine escapes unburned.
As a result, manufacturers moved towards direct fuel injection systems to enhance the efficiency of these engines. These systems spray the fuel into the combustion chamber using precision injection timing, with the piton covering the exhaust valve to prevent any fuel escape, improving the motor’s efficiency.
The four strokes per engine cycle, exhaust, and intake occur separately with four-stroke motors. DFI systems tend to be markedly more efficient than two-strokes due to the improved cycling of the pistons and computer management over the valves.
However, it’s important to note that the improvements in fuel injection and engine technology mean that the new generation of two-strokes is almost as efficient and quiet as four-stroke motors.
An example is the Evinrude E-TEC two-stroke DFI motor. This engine injects fuel at twice the speed of standard models, adjusting fuel delivery and the oil-gas mixture required by the onboard engine management system.
The result is an engine with all the power and performance of a four-stroke while running far quieter than traditional two-strokes.
The general reason behind using a two-stroke is that it’s more affordable than the four-stroke, and it offers more power due to the two-piston cycles per engine cycle. However, recent tech developments on four-strokes improve the power and performance of the four-stroke while maintaining efficiency and quiet-running.
As a result, the decision between choosing a two-stroke or four-stroke motor is now a function of what you want to do with the boat and your budget. We all want a four-stroke, but some of us might not have the extra money for it.
With modern DFI two-stroke engines, you get a motor that offers all the performance and efficiency of a four-stroke, with the speed and power you need for powerboating and watersports.
- Two-stroke DFI engines offer you a lighter motor with almost the same efficiency and quiet-running capability as a four-stroke.
- While four strokes are generally quieter, the DFI two-stroke advancements mean that they run at nearly the same decibel output.
- Two-strokes provide the motor with a better holeshot, but four-strokes are closing the gap to gain the same power and performance as DFI two-strokes.
Buying Your Outboard Motor – New or Used?
Like buying a car, you have options to choose a new motor or buy pre-owned engines. When you’re at the dealership, it’s tempting just to add a new motor to your purchase, but you might find a pre-owned motor for half the price, offering you the same performance and service life as a new engine.
However, when you’re buying pre-owned motors, you’ll need to know what you’re looking at when assessing the engine.
If you don’t have any mechanical experience working on boat motors, we suggest you bring along a qualified and experienced mechanic to the viewing. They’ll assess the condition of the engine before you close the deal.
Calculating Outboard Motor Capacity for Your Boat
If you have a 40-foot cabin cruiser, your motor capacity is going to be much higher than for a 16-foot bowrider. So, how do you choose the right motor capacity for your vessel? The sales agent will likely recommend the right motor for your boat if you’re buying from the dealership.
However, if you’re searching on the used market, you’re going to need to do a quick calculation to figure out the right motor capacity for your vessel.
You’ll need to start the calculation by converting the vessel’s weight from tons to pounds.
So, if your bowrider has a dry weight of 1.1-tons, it works out to 2,500-lbs.
For the average performance model boat, like a center console or a bowrider, you’re going to need approximately one horsepower (HP) for 25 to 40-lbs of weight.
Take the boat’s weight in pounds and divide it by 200 (for a 200-HP engine). So, for our 2,500-lbs boat, we get approximately 12.5-lbs of horsepower per pound with a 200-HP engine.
2,500 divided by 125 is 20-HP per pound, and the lower the figure, the higher the engine’s performance. So, dividing 2,500 by 300 gives us 8.33 Hp-p/lb, making for a fast boat that’s ideal for watersports and speed boating.
Why Should I Choose a Larger Outboard Engine?
The motor capacity defines the boat’s power and its performance on the water. If you’re facing a choice between an engine that’s slightly under the recommended capacity or slightly over, we recommend going with the higher power to avoid disappointment out on the water, especially if you’re into watersports or speed boating.
If you have a pontoon boat or slow-moving cruising vessel, then the lower capacity is the better choice as these models do not have the design for high-speed operation. Overall, we recommend going with the higher power if you enjoy watersports and offshore fishing and lower capacity option for inland water bodies and cruiser boats.
What are the Top Features to Look for In an Outboard Motor?
After calculating the right motor capacity of your boat, it’s time to assess the engine’s features. Here’s what you need to look for when choosing the right motor for your vessel.
Ripcords are so 1990s. Today, all the leading motor models come with an electronic start. You either turn a key or push a button and the motor springs to life, with no ripcords required.
When the water is rough, and you need a fast start, electronic ignition can mean the difference between taking water onboard or making a quick escape from the weather conditions.
Choose a motor offering you power tilting of the engine. This feature electronically lifts the propellers out of the water by tilting the motor forward at the push of a button.
It’s a great feature for fishing in shallow waters to stop the props from agitating the sediment on the bottom, and it also helps with lifting the motor when you’re launching or trailering the vessel.
This feature is like a “nitrous-oxide canister” in a sports car. It increases a temporary surge of power to the motor to combat strong currents and winds out on the water. The thrust increases the forward propulsion by up to 15% and the reverse propulsion by 60%.
The power thrust also assists with the maneuverability and steering of the boat, making it easy to reach top speeds while maintaining full control of the vessel in demanding water conditions.
Is A Dual Outboard Setup the Best Choice?
Take a drive through the marina, and you’ll see boats with single, double, or even triple outboard motor configurations.
Typically, these engines feature on boats that take to deep water for sports fishing trips. In most cases, the captain won’t use two or three motors simultaneously; they keep the auxiliary motors as a backup in case of mechanical failure of the primary engine while they are out at sea.
Installing a dual-motor configuration to your boat also makes docking that much easier. The propellers revolve in separate directions, allowing for the easy repositioning of the vessel as you approach the dock or slip.
However, if you install dual or triple motors to your boat, it will double or triple the expenditure you make on the motor purchase. You’ll have to decide if the addition of extra engines offers you enough value to justify the increase in your budget.
If you have the budget, a twin outboard setup will always be the optimal choice for most boating applications. It’s important to note that a dual or triple configuration is only useful against mechanical failure if each motor has an independent fuel and power system.
You might find that it’s way more affordable to get a single motor and just upgrade your marine radio system so you can call for rescue if the engine breaks down while you’re out at sea.
Do I Need High-Octane Fuel for the Outboard Motor?
As high-compression motors arrived in the boating industry, early models would experience the fuel combusting too early in the combustion cycle. This pre-ignition problem, otherwise known as “spark knock,” was an irritating noise, and it also damaged the combustion chamber, scarring the cylinder walls and damaging the valve seats.
As a result, manufacturers included additives in fuel to slow the ignition until the spark plug was ready to ignite the fuel. So, today’s modern engines now operate better with high-octane performance fuels, allowing them to handle the higher compression rate.
However, the reality is that using high-octane fuel on your outboard motor isn’t the best choice – for your wallet. These high-octane fuels don’t add any additional performance to the outboard motor, and you’ll get the same power out of using 87-octane as you would with other grades on the 90s.
With the cost of fuel rising in the United States and some states seeing prices at over $4 a gallon, using a lower octane fuel will save you hundreds of dollars over the year.
How Do I Select the Right Propeller for My Outboard?
You can think of the propeller on your boat like the tires on your car; it’s where the “rubber meets the road” or, in our case, where the “steel meets the water.” Props are similar to tires in that they come in different designs for different purposes out on the water.
You have dedicated props for performance speed racing, watersports like wakeboarding, and increasing economy. If you’re purchasing your new motor for the dealer, ask them about the prop installed on the engine and the various prop options available.
Most dealers install efficient, mid-range performance props on their motors. So, if you’re buying a boat specifically for watersports, this prop might not be the best option for the task. However, you can negotiate with the dealer, and they’ll likely install any type of performance prop you want on the engine.
Fortunately, understanding propeller technology isn’t rocket science. Props change the pitch and diameter of the blades to suit different applications in the water. As you already guessed, the diameter refers to the size of the prop.
The pitch refers to the theoretical distance the prop needs to travel in a complete revolution, provided there is no slippage. The reason why you need to select the right prop for your boat comes down to the fact that motor manufacturers rate an engine’s horsepower at specific RPMs, setting the rpm range for the motor’s top-end operation.
However, the motor can only reach this top-end range if it has the right prop suited to the task. If the prop permits the engine to over-rev, you risk damage to the motor due to the high-revs creating a faster rate of wear and tear on the motor components.
Conversely, if the prop is too large, then the motor will struggle to reach top-end rpm ranges, creating another set of challenges for the engine that might damage its internal components.
Picking the right pop pitch ensures you get the best performance from the engine while protecting the internal components from damage. To test the prop., you’ll need to take the boat out onto the water and open the throttle to the full position.
When your engine runs over the max-rpm range, back off the throttle, reduce speed until the rpm gauge drops to the suggested rpm range recommended by the manufacturer. When you return to shore, check the pitch of the props.
You should have a drop of 200-rpm for each degree of increase in the pitch. Cupped props can reduce rotation by up to 200-rpm. Ask your dealer if they allow you to test the prop. Most dealers will agree, provided you return it to them undamaged.
As long as the propeller reaches the top-end range, but doesn’t exceed the max-rpm value, delivering wide-open RPMs to the bottom of the recommended range provides you with better performance in holeshots. Props offering RPMs toward the top-end of the range generate higher top-end speed.
What to Know About Boat Engine Propellers
The condition of the propeller is more important than the type of prop installed on the boat. Damaged propellers can cause problems with the normal operation of the engine, creating stress in the motor components that cause damage.
We recommend going with stainless steel propellers as they offer you the truest running performance and high strength levels. Aluminum is a cheaper material, sacrificing itself to provide the lower unit better protection.
Four-blade props beat three-blade models in the time it takes to reach planing speeds, midrange speeds, and they offer you better low-speed handling.
Easy Outboard Engine Maintenance Tips
When the motor isn’t in use, keep the fuel tank topped to reduce the chances of condensation building on the inside of the tank. If water gets into the engine system, it will require you to bleed the system to get the motor to start.
- Add fuel stabilizer additives to the fuel tank every time your refuel. It’s critical to do this with ethanol-based fuels to prevent separation and fouling of the fuel system.
- Inspect your propellers after each trip for damage, dings, pocking, and wear.
- Inspect the hoses and fittings to ensure there are no leaks.