One Engine or Two? Which is right for me?

When you’re in the market for a Cruising Boat, one of the many decisions to consider is whether to choose a single-engine or twin-engine vessel. Each option has its advantages and disadvantages, often influenced by factors such as your boating style, budget, and personal preferences. Let’s take a closer look at the financial aspects of each type, including purchase price, operating costs, maintenance, and insurance. We’ll also discuss performance and practical considerations.

The only rule is that there are exceptions.

Now, before we get into it, let me reiterate that there are ALWAYS exceptions when talking boats. I’ll be talking about the most common variations. For example, most boats don’t fly, but yes, there are a few that can! So, please don’t roast me in the comments about the exceptions to the rules!

Boat Type: Sometimes You Don’t Have A Choice

If you’ve chosen a sailboat, you are probably going to have a single engine (or an outboard motor). On the other hand, if you’ve chosen a catamaran (either sail or power), you are probably going to have two engines, one in each pontoon.

If you want to operate your boat using a joystick, you are most likely looking at Pod Drives. Due to the nature of the technology, you will have a twin-engine boat. Note: Some boats use a combination of twin engines, bow and stern thrusters, and computer wizardry to allow joystick control.

Most new cruiser-class boats have twin engines. The market for Cruisers is typically focused on fast boats, and manufacturers have changed their designs to meet that need. Cruisers Yachts, Princess, and Tiara all only offer twin-engine designs in their new models.

Single-engine designs are much more prevalent in the Trawler style. Several manufacturers offer new single-engine models, like Beneteau’s Swift Trawler 35, Kadie-Krogan, Great Harbor, and North Pacific. The smaller Tug-style boats, like Ranger, American, and Nordic Tug, also offer single-engine models.

The Speed Factor: Twin Engines don’t necessarily mean fast.

There are single-engine boats suitable for cruising that can reach speeds in excess of 20 knots. The Beneteau Swift Trawler 35, with its 425hp Cummins engine, can reach 20 knots, and the Ranger Tug R-21 CB also has a top end of 20 knots.

The opposite is also true. Some boats, especially larger Expedition Trawlers like Nordhaven and Marlow, have twin engines, yet their top speed is under 10 knots. It’s all about size, hull design, and fuel efficiency. Some Expedition trawlers like Nordhaven and Bering have a single main engine and a secondary smaller auxiliary or “get me home” engine.

Another benefit of twin engines is that you can limp along on one engine if one goes down. This is highly dependent on what went wrong. Both engines will probably quit if it is bad fuel (or out of fuel). But with mechanical issues, you may be able to use one engine. Before you try this out on the water, you need to understand that 1) it is hard to control the boat’s direction; it wants to go in circles. 2) In many transmission designs, you need to clamp down the dead engine’s propeller shaft so that it doesn’t spin as you move, damaging the transmission. This means pipe wrenches and strapping.

We had a transmission go out in Fernandina Beach, FL, and ran on a single engine all the way to Georgetown, SC—a little over 300 miles! Was it fun? No, but we made it to our mechanic. It takes some practice and preparation so that you don’t damage transmissions, but it can be done.

Purchase Price: The Initial Investment

When it comes to purchase prices, single-engine boats usually cost less upfront than their twin-engine counterparts. This is mainly because twin engines have, well, two engines. The engines, transmission, and supporting infrastructure are some of the most expensive components in the manufacture of a boat. And you are buying two of everything with a twin-engine boat.

The lower initial investment makes single-engine boats especially attractive for many new buyers. However, the price difference can be significant when looking at larger twin-engine vessels, particularly those designed for higher speeds or heavier loads.

Operating Costs: Fuel Efficiency Matters

When it comes to operating costs, single-engine boats have the upper hand. Their simpler design results in better fuel efficiency. This advantage is due to the reduced weight of only one engine, leading to lower fuel consumption. On the other hand, twin-engine boats, while providing better performance, carry the additional weight of two engines and the fuel they require, resulting in higher fuel expenses.

However, just because a boat has two engines doesn’t mean it is not fuel efficient. Many Expedition Trawlers, such as Nordhaven and Marlow, have twin engines. However, they are designed for long-range cruising at lower speeds and, looking at gallons per mile, are more fuel-efficient than their fast cousins.

Here are a few popular Cruising Boats of various styles and their fuel consumption.

Maintenance Costs: The Price of Complexity

When it comes to maintenance, single-engine boats generally have lower costs due to their simplicity. With only one engine to maintain, repairs are easier and cheaper. Conversely, twin-engine boats require double the maintenance work, part costs, and labor. You’ll need to keep an eye on two engines, two fuel systems, two transmissions, and two propellers, all of which can significantly complicate and increase routine maintenance expenses.

Holding You Back: Propellers, Running Gear and Damage Exposure

With single-engine boats, the propeller is centered on the boat and is usually protected by the keel that runs down the middle to give the boat directional stability. This gives some protection to the propeller if you hit something in the water or become grounded. The keel will typically hit whatever it is first and protect the running gear.

Anything sticking out from under the boat will induce some degree of drag, slowing you down in the water by creating resistance and disrupting the smooth flow of water around the hull. The “Running Gear” (propellers, shafts, struts, rudders) also induce drag. On single-engine designs, the keel helps alleviate some of this drag as the keel reduces the amount of exposed running gear. Many sailboats have folding propellers to further reduce drag when the boat is not using the engine.

It is said that there are three types of boaters, those who have run aground, those who will run aground, and liars.

Twin-engine boats typically have more exposed running gear. Along with two engines, two propellers turn in opposite directions and give you the propulsion that moves you forward. In most twin-engine designs, the propellers and associated running gear are positioned on opposite sides of the center keel. This arrangement provides much less protection, so drag increases, reducing performance. The lack of a keel in front of the propellers and running gear to protect them also leads to a higher risk of damage in the event of grounding or striking debris in the water.

Pod Drives: Higher Complexity & Higher Cost

Pod Drives are a highbred design where pods which drive the propellers extend down on either side of the keel and have dual counter-rotating propellers. (Yes, there are two props per pod!) In the case of the Volvo IPS Pod drives, the propellers actually face forward. This design reduces drag and increases performance.

Pods are complex items with lots of gearing, requiring oil changes and having rubber seals that need to be replaced to keep out seawater. All of this requires annual maintenance that can add an additional $2,000 to $3,000 to your annual maintenance bill. Similar to twin-engine propeller-driven boats, the pods are exposed. They are designed to separate from the boat in the event of a significant impact so that they don’t rip the bottom of the boat out. Replacing a pod drive is a very expensive proposition, and can cost $20,000 to $30,000 or more.

Insurance Costs: Higher Value & Higher Performance

The primary factor in boat insurance costs is the “hull value” or what the insurance company will pay you if the boat is a total loss. The higher the hull value, the higher cost to insure. In addition to the hull value, insurers look at the cost to repair if the boat is not a total loss. I am not an insurance expert, so I won’t get into details, but in general terms, the more complex a boats systems, the higher your rates will be. Single engine boats cost less than twin engine boats. Twin Pods cost more to repair than twin conventional drives so rates increase. You get the picture.

The other side of insurance cost is liability insurance. In very general terms the faster the boat, the more likely there is to be an accident of some type, so the higher the insurance will be. Rates, coverages, and costs vary widely from insurer to insurer, state to state, and boat to boat. Make sure to talk to an insurance agent as part of your boat buying process to get an idea of your annual insurance costs in advance of choosing a specific make/model.

The Need for Speed: Understanding Motive

Ultimately, while some twin-engine pleasure boats might be marketed as “fast boats,” many are large vessels that require two engines simply to adequately handle their weight and ensure stable performance in various conditions. This necessity underscores a broader point: the desire for extra speed is often the most compelling reason for those choosing twin engines. However, it’s crucial to recognize the full scope of what this decision entails; your thirst for speed comes with not only an increased financial investment—be it through purchase price, operation, or maintenance—but also a commitment to mastering the handling and decision-making that comes with the territory.

If you are going to be cruising in open waters like off-shore or in larger bays, a faster boat may offer significant advantages. For Cruisers planning on making the 7,000-mile Great Loop, bear in mind that while there are open waters, much of the Loop follows the congested Intra-coastal Waterway, and is in canals, creeks, or shallow and built-up areas. Many of these are no-wake zones and have speed limits. Having a boat with better fuel economy versus a fast boat can be a better choice for long-range cruising. With Diesel averaging $4.70 per gallon, save even a 1/4 gallon per mile, and that’s about an $8,000 savings over the course of the Loop!

Conclusion: Making the Right Choice

The choice between a single-engine and twin-engine pleasure boat largely hinges on personal preferences and boating habits. If you prioritize speed and performance, twin engines offer undeniable advantages, but this comes with higher costs and increased maintenance responsibilities. On the other hand, single-engine boats present a more economical option, both initially and in ongoing expenses, making them a solid choice for casual boaters or those looking to maximize fuel efficiency. Ultimately, it’s essential to assess your boating goals, experience level, and financial readiness before diving into your purchase. With careful consideration and a clear understanding of your needs, you’ll be well-equipped to make the right choice and enjoy countless memorable moments on the water.

What type of boat do you desire? Slow single, Fast Twin, Long Range Expedition?
Let us know it in the comments below!

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