The popularity of outboard-powered multihull (aka catamaran, or cat) fishing boats has grown tremendously over the past few years as increasing numbers of boatbuilders enter this market. Yet, traditional monohull fishing boats still hold their own. As an angler looking to buy a new boat, it’s nice to have choices, but it also adds a new dimension to the decision-making process.
Ultimately, however, you are bound to ask: Which one is the best for saltwater fishing—a cat or monohull? The answer hinges on a number of factors and your personal angling preferences. Let’s look at the key factors.
“A strength of the catamaran is that it has such low drag,” says Gino Morrelli, catamaran designer, whose design credits span from America’s Cup contenders and Olympic-class cats to power cats for charter use, up to a record-setting round-the-world 125-foot cat. “It’s just basic hydrodynamics: Two slim hulls have very low resistance. They push much less water than one wider hull and therefore require smaller engines and increase efficiency.”
If you’re thinking about a single outboard engine, you can stop thinking about buying a cat. By virtue of the design, nearly all cats must be powered by twins or quadruple motors—no singles, no triples, no quintuples. For any of these latter outboard configurations, you’ll need a monohull, which can also accept twins and quads. Now that we have that simple fact established, let’s look at additional factors to consider when shopping for a new fishing boat.
Cats can provide a softer ride than a monohull in a seaway because their knife-like hulls easily slice through the waves rather than crush them. “Two sharp hulls pound less in a seaway too,” Morrelli says. Cats also tend to remain flat throughout their speed range. On the other hand, monohulls—especially deep-V hulls—tend to experience bow rise when accelerating, though step-hulls have less bow rise than conventional V-hulls.
The ride between cats and monohulls differs in other ways. For example, the motion of a catamaran in waves is more like a cantering horse, which some people like and others don’t. At low speeds in a beam sea, some power cats can have a sharp roll as swells pass under each hull separately, but monohulls also roll considerably, which is why gyrostabilizers have become popular aboard them. But the roll moment is different for each, and you might prefer one motion to the other.
That said, the inherent stability of the catamaran design rolls less with the seas, making fishing offshore less tiresome and more comfortable. Available from 20 to 48 feet, catamarans typically offer a large fishing platform with generous storage and fishing amenities. They are available in a wide variety of deck layouts, including center-consoles, dual-consoles, and even pilothouse and express variants.
In hard turns, many catamarans remain flat or even lean outboard somewhat, which can intimidate inexperienced skippers more used to the inboard bank of a monohull. Handling is another factor to consider, and catamarans have both good and bad features. With the engines widely spaced in the two hulls, a catamaran is more maneuverable at slow speed and spins easily by using its engines. A monohull, with the two engines close together, requires more power and technique to spin.
The downside of handling a cat is the much wider beam: Turning a platform that is more than half as wide as it is long can take planning, especially in narrow channels. That wide beam has another downside: It might not fit into many marina slips, which means with a cat, you might be relegated to end ties (with more wave motion) or on side ties along a seawall. Catamaran slips are often more expensive too. With monohull saltwater fishing boats, the beam is narrow enough to fit into most any marina slip.
Some, but not all, cats also have weird quirks, such as “sneezing” between the hulls when running in some conditions, which sends spray over the bow, and also pounding at times at idle speeds due to air pockets between the two hulls. Draft is something else to keep in mind, especially if you want to explore shallow waters. All things being equal, a cat hull generally draws less water than a comparable monohull.
That wide beam of a cat offers upsides, including more deck space for fishing. The generous room carries well forward, rather than narrowing toward the bow, as is the case with monohulls. However, if you are looking for maximum headroom in a center-console interior, a monohull is usually the better choice. That’s because the depth along the centerline of a monohull can more easily accommodate a step-down console interior. A cat, however, has no virtually no room along the centerline for a step-down console interior. That’s because, as you might imagine, it needs plenty of room between the hulls in order to allow the seas to pass underneath the boat.
Fact is, a cat has practically no room for insole storage lockers, fish boxes or livewells along the centerline as does a monohull fishing boat. However, the room within each hull of a cat is often immense, so this is where builders usually locate insole fish boxes, fuel tanks and dry-storage compartments.
That brings us to personal preference when it comes to style. Early cats—the ones introduced in the 1980s and ’90s—were a tad boxy, and that lack of streamlined styling turned off many potential buyers. A number of boatbuilders took heed, and in recent times have integrated sleeker sheerlines to cats—so much so that when viewed in profile, it can be difficult to discern a cat from a monohull at a glance. Yet, from other angles, the two still look different. Some boating anglers prefer the classic look and flaring bow of a monohull; others see new beauty in the design of a cat.
Cat or monohull—which is best? There’s no perfect boat. But by weighing upsides and downsides, and taking a demo ride in each, you might find among the two types of boats one that is perfect for you.
Symmetrical vs. Asymmetrical Cat Hull Design
When shopping for a catamaran-style saltwater fishing boat, you might come across the term “asymmetrical hull design.”
While you might infer that the two hulls are of different size and shape, the term actually refers to the differing shapes of the inner and outer walls of the two hulls. The concept becomes most apparent when viewing a cross-section of the hulls.
One example of this design approach is the running surface of the -Invincible 40 cat designed by the Newport Beach, California-based marine architectural firm of Morrelli & Melvin. The same -design principle has been incorporated into a -number of other Invincible cat models.
The design is officially known as a hybrid semi-asymmetrical catamaran hull. “This asymmetrical shape allows the boat to lean inward while cornering, versus cat hulls with symmetrical cross-sections that tend to turn flat or lean outward in turns,” explains Pete Melvin, a principal in the Morrelli & Melvin design firm.
The Invincible 40 also features two steps in each hull. Steps represent a fairly common design element of many of today’s monohull saltwater fishing boats, but an increasing number of cats also now feature steps, which ventilate the water rushing under the hull while underway to increase lift and efficiency.
With computational fluid-dynamic engineering (continued on page 24) software, the design team at Morrelli & Melvin is able to test numerous running -surfaces before construction of a boat ever begins.
“This allows us to refine the placement and design of a twin-step to maximize lift and efficiency,” Melvin explains.
In addition to the steps and asymmetrical hull design, a specially engineered pod above and between the hulls helps split the water that rushes through the tunnel in the middle of the sponsons while underway.
This element serves to further soften the ride by aerating the water and -creating an air cushion as the boat descends off a wave.
Not the confuse things, but getting back to our original premise, there actually exists power catamaran boat models with hulls of different sizes.
The most startling examples come from Aspen Power Catamarans based in Washington state. The hulls of Aspen boats like the C108 are not a matching set. They’re asymmetrical.
An Aspen’s starboard hull is wider than its port hull. The thinner hull generates less drag. At the same time, each hull offers a balance between displacement and load, and that keeps the boat stable. The asymmetry goes largely hidden, except for one obvious element.
The C108’s two outboards are not identical. On starboard is a Yamaha F200, on port an F115. Both engines share the same rpm range, and each is propped proportionately. This allows the C108 to run straight and bank flat when turning to starboard, but lean slightly outward in turns to port.
