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Powerboats
Powerboat hull shapes, common types and engines; all you need to know to get started.
April 23, 2018
The world of powerboats can seem a bewildering one to a newcomer. Even someone who has been involved in boating all their life may well find themselves needing to understand more when their lifestyle or budget changes. This basic guide aims to outline all the major powerboat types and features.
If you’re the kind of boater who doesn’t want to rely on the wind for propulsion, a powerboat is plainly the way to go. However, given that the market comprises everything from a 10-foot outboard-propelled inflatable tender to a 600-foot megayacht with on-board helicopter, it can be useful to understand a few basic principles before deciding upon the kind of boat that best suits your needs.
The sheer variety of powerboat types can be bewildering.
Powerboat hulls
Hull form: displacement or planing
For most leisure powerboaters, there are three primary hull forms to consider - displacement, semi-displacement and planing.
A full displacement hull has to displace its own mass in water in order to move forward one boat length.
By contrast, a planing hull is a platform that uses a combination of lighter weight, greater relative power and extra lift from water flow over its contours in order to skim across the surface.
Those in pursuit of sedate but efficient long-distance operation tend to go for displacement hulls; those keen on rapid, agile, short-distance sport will go for a planing hull; and those who want the benefits of displacement with a little extra speed often look toward the semi-displacement camp.
Monohulls versus multihulls
The number of hulls used is also crucial. The monohull is by far the most prolific type of powerboat, probably on account of its affordable construction costs, its attractive looks and its reassuring popularity.
However, assuming you can afford the initial outlay and the berthing costs, there are some extraordinary benefits to the twin hulls of a catamaran. They are more stable at rest, flatter through the turns and easier to manoeuvre at low speeds in tight marinas. They also offer more space, a softer ride, greater directional stability and radically improved fuel efficiency. Their effectiveness has seen them thrive in the offshore commercial world but for now, their cost and their sedentary image has radically restricted their prominence in the leisure market.
Hull shape
By far the most prolific leisure powerboating hull form is the planing monohull and the basic paramaters of a given shape reveal plenty about its intended use.
For instance, if you look at the relationship between beam (the width of a powerboat) and length, relatively long, narrow hull shapes are usually about speed, sport and ride softness. On the other hand, broader, shorter hull shapes are usually about inboard space, easy planing efficiency and versatility of application.
More acute deadrises and angles of entry are often the preserve of the former, but it is a common fallacy that acute hull angles make for a better boat. On the endurance powerboat racing circuit, they might certainly help, but the idea of a ‘better boat’ is always a direct function of the job to which it is put - and on most family boats, the primary function is not outright pace through heavy seas but safe, efficient, reliable and flexible summer entertainment - precisely the job that a great many broader, shallower leisure platforms are designed to carry out.
Narrow-beamed rocket ships with big power and stepped hulls are very sexy but there are plenty of hull shapes that make more sense.
Hull construction material
As for the building materials, fibreglass remains by far the most prolific on the recreational market and you can see why. It is very clean and attractive and resin infusion helps further improve the strength, reduce the weight and create better consistency of finish. However, it’s by no means the only (or the automatic) choice.
For instance, while polyethylene is not especially pretty, refined, lightweight or cheap, it is resistant to delamination (see Plastic boats: polyethelene boat construction). It will also happily take the repeated beatings of everyday family boating and, because the pigment runs throughout the material, even a deep scuff is easily fixed. For small, hardworking knockabout boats, it puts forward a very strong case, but arguably, aluminium is even more versatile.
Aluminium is light in weight, high in strength, easy to live with, simple to mend and ecologically sound. It can be a little noisy underway from the water slapping at the hull and some people dislike the slightly rudimentary look of the welds but its striking success in Scandinavia, where leisure boaters use their boats every day of the week, is testament to the rigorous effectiveness of the material.
If the finish of aluminium really doesn’t appeal to you, however, there are now several builders who offer a fusion of aluminium hull and deck with fibreglass topsides. For the consumer, that promises not just the practical benefits of aluminium, but also the glossy showroom finish of GRP.
Powerboat types
Every boat is a set of compromises designed to optimise its performance in some respects at the inevitable expense of its performance in others. And just as the hull shape gives you plenty of clues about that intended design direction, the internal layout also tailors a boat to the needs of a given user.
Though there are plenty of boats that straddle and bend the boundaries (like the twin-hulled, hydrofoil-equipped Hysucat RIB, the C-Fury, the Zego or any number of amphibious craft), the basic powerboat brackets can be broadly covered by the following…
At its simplest, the tender is a compact, workmanlike water taxi.
Tenders
A tender is a boat used to ferry people and equipment from a larger mother vessel to shore and back. While a tender for a superyacht can be an exotic, high-performance 30-foot plus offshore craft, the most common form of tender is a compact inflatable boat with a modest portable outboard engine that can be stowed, deployed and recovered with ease. Inflatable tenders come with PVC or Hypalon construction (PVC for lighter weight and lower prices; and Hypalon for extra durability); and an inflatable or rigid floor (inflatable for low weight and easy assembly; and rigid for higher performance applications).
The personal watercraft is all about big fun on modest money.
Personal watercraft
A PW or PWC (often incorrectly referred to as a Jetski, see Personal Watercraft) is a compact platform in either stand-up or sit-down format. Capable of carrying anything from one to three people, it employs jet propulsion for thrust and it uses handlebar-style grips with trigger-operated throttle for easy, intuitive operation.
Acceleration on a modern sports PW can be fiercely rapid, with a degree of poke and urgency unmatched by any conventional powerboat – and happily, the user interface, particularly on the latest Sea-Doo fleet, is well equipped to help you make the best of that performance, with various manoeuvring aids and even the option of a suspension-equipped seating and console unit to help mitigate the impacts.
The bow rider remains the archetypal fair-weather family day boat.
Bow riders
The bow rider is a particularly prolific style of day boat available in a variety of forms. The classic American-style family bow rider comes with communal cockpit seating plus additional loungers on a V-shaped seating arrangement in the tapered bow.
The Scandinavian bow rider reacts to the region’s cultural boating dynamic by sacrificing the additional bow seating for extra deck space, dedicated boarding points and a step-through bow with elevated rails.
The specialist watersports platform uses a regular bow-rider layout, but with some specialist tweaks, like generous inboard power, directional fins, uprated ballasting features to help control the wake shape and a range of pursuit-specific add-ons that can radically increase the price as well as the ability.
The modern RIB is much more than just a commercial tool.
RIBs
A RIB (or Rigid Inflatable Boat) is a vessel with a rigid hull and an inflatable collar wrapped around its perimeter. Originally designed as a serious sea boat for commercial applications and heavyweight load carrying duties, the modern, style-conscious leisure RIB tends to use inflatable tubes of lower diameter, alongside greater power and broader versatility of application. However, RIBs remain great favourites as patrol vessels, safety boats, support craft and powerboat tuition platforms. While a good RIB remains a fine companion in a tough seastate, the key failing of the type for the leisure boater is a relative lack of inboard space.
Every cruiser treads a line between internal accommodation and sporting ability.
Cuddies and cruisers
The basic difference between a cuddy cabin powerboat (a small, sporting cruise boat with compact accommodation for two) and a sports cruiser (which comes with at least one additional guest berth) is of course the size. However, the conventional ‘open-cockpit-closed-bow’ layout generally employed by these craft is by no means the only option.
There are some lovely aft cabin cruisers on the market, where the main cabin is loaded into the spacious back end instead of the bow’s tapering ‘V’. There are also plenty of trawler style craft, usually quite traditional, semi-displacement distance-makers with upright topsides to maximise internal capacity. There are also some famously capable 'walkaround', four-season vessels (like Scandinavia’s Targas and Sargos) that combine authentic seagoing hulls with real seamanship practicality and compact but carefully managed internal spaces. Whichever form you favour, you need to decide whether the ‘sports’ bit or the ‘cruiser’ bit matters most, because generous accommodation and sparkling performance are rarely harmonious bedfellows.
With its bow flare, sheltered helm, deep gunwales and big cockpit, the fast fisher is also a very sound family choice.
Sports fishers
From 16-foot fast fishers to vast, 80-foot, multi-deck offshore platforms with fighting chairs and observation towers, the sheer variety of sports fishers reflects the passionate dedication of sea fishing fans around the world. However, all good sports fishers have several things in common: a broad beam for extra internal space and stability at rest; a generous bow flare to help protect the occupants from spray; an acutely angled forefoot to help soften the impacts; and a bow shape with sufficient buoyancy to resist a stuffing at low speeds.
You also tend to get a wide-open cockpit with deep secure gunwales and a central helm to provide shelter from the elements without inhibiting deck space or passenger movement. Perversely, these core sports fishing traits also make a well-sorted sports fisher a remarkably effective companion for the non-specialist family boater. See How to pick the perfect boat for fishing, Five top sports fishers and Fishing boats: a buyer's guide.
The world of custom superyachts is all about bespoke one-upmanship.
High-end custom craft
As the size, the complexity and the features of a powerboat develop, so the parameters change. Motoryachts give way to superyachts and superyachts give way to megayachts - and as they do so, the standard, market-ready, factory-fit vessel gives way to the bespoke, one-off, custom creation. Competitive one-upmanship is a key driving force among the world’s wealthiest boat buyers and as a direct result of that, the most extravagant megayachts can now extend well beyond 500 feet and (depending on the fit-out), well beyond £400 million.
Powerboat engines: propulsive options
In the broadest terms, a marine engine comes either as an inboard engine or an outboard engine. In inboard form, it either sits right at the stern, operating through the transom by means of a sterndrive; it sits further forward and operates via a fixed shaft that exits through the bottom of the hull; or it is hooked up to pod drives - integrated steerable pods, comprising transmission, outdrive and props, which protrude directly through the hull. As the name suggests, an outboard differs in that it is positioned further up and further out, on top of the transom itself. As you might expect, the various methods have very different strengths and weaknesses…
Shaft drive remains a big favourite on serious watersports platforms, where secure grip, a central pull and balanced weight distribution are crucial. It is also valued on a great many larger craft where the reduction in inboard space is balanced by the reliable simplicity of a fixed shaft and a rudder for steerage.
You do of course lose the capacity to amend the attitude of the boat by trimming the leg, but the positioning of the engine’s mass low down and toward the centre of the hull does a lot to help maximise ride comfort. Whether the gains in running efficiency and internal space (not to mention the delightfully intuitive joystick interface) of pod drives will see them supplant shaft drives on express cruisers, where they appear to be in their element, is currently a matter for debate.
With ever-increasing power outputs on outboard engines, the choice between sterndrives and outboards on midsized sports cruisers is also a matter of particular interest. There are those who swear by diesel sterndrives even on relatively small boats, due to the efficiency gains and the superior weight distribution. The trouble is that you need to do at least a couple of hundred hours a year to offset the additional purchase price of the diesel route, so if you can get the weight distribution right, the outboard approach is still likely to provide the more affordable ownership experience - and as the new Flipper 880ST illustrates, it can also create an astonishing level of inboard versatility on even a modest family cruiser.
Electric and hybrid engines
On a similar note, there are now various electric and hybrid solutions around, some of which go beyond the flattering of eco-conscious sensibilities to enable relative self-sustainability and increased cruising independence. However, while large, heavy, expensive battery banks can make good sense for the commercial operator who puts endless hours on his boat, for most users and most vessels, internal combustion remains the most efficient means of primary propulsion. Certainly, the light weight, compact size and unmatched cleanliness of electric outboards makes them excellent as auxiliary motors, but don’t let anyone tell you they are silent because they’re not. Imagine a whining hum somewhere between a medical implement and a mosquito in a box and you’re probably somewhere close.
Jet power is plenty of fun and very practical for shallow water operation.
And so we come to the final mainstream propulsive method for leisure boaters - the jet drive. A jet operates by sucking water through an intake grate and blowing it out under pressure through a directional nozzle. The fact that it pushes water against water makes it inherently less efficient than a propeller (which operates directly upon its medium), but it does have several major benefits that make it particularly effective as a leisure choice. For instance, the absence of a propeller makes it ideal for shallow water operation and (once you get the hang of it) its close quarters manoeuvrability is also a pleasure. They can be great fun to drive at pace too and with a simple bucket over the nozzle to direct the jet from forwards to astern (instead of a gearbox), the engine also tends to enjoy a relatively easy life.
The Recreational Craft Directive
Though it certainly has its critics, not least among boat builders themselves, the Recreational Craft Directive (RCD) is a useful yardstick in helping the consumer understand the general purpose for which a powerboat is designed.
There are four categories (A, B, C and D), based on the wind and wave conditions likely to be encountered in a variety of boating environments (‘Ocean’, ‘Offshore’, ‘Coastal’ and ‘Sheltered Waters’). It’s a useful system to keep in mind, but more useful still is to take responsibility for finding the right powerboat by assessing your own needs and picking a hull, building material, power solution and layout design that best caters for you, your family and your favoured pursuits.
For more on buying a powerboat, see our special guide.
The size, hull shape, furniture arrangement, building material and propulsive method-are all best governed by the intended application.
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