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Boston Whaler 405 Conquest (2020-)

4 x 400-hp Mercury Verado Joystick PLT

Brief Summary

The Boston Whaler 405 Conquest is a versatile boat that can take a family fishing or cruising with a spacious cockpit, convertible seating on the helm deck, and a cabin that can sleep up to six. Power is provided by quad Mercury outboards up to 400-hp each.

Key Features

  • Quad outboard motors
  • Spacious cockpit with summer kitchen or livewell in stern
  • Convertible dinette seating
  • Full-width windshield with twin opening vents
  • Foredeck sun pad
  • Private bow stateroom

Test Results

600 3.6 3.1 2.5 1.4 1.3 778 676.2 64
1000 6 5.2 4.4 1.4 1.2 739 642.3 66
1500 7.8 6.8 7.1 1.1 1 597 519.5 70
2000 9.9 8.6 11.3 0.9 0.8 473 411.4 73
2500 11.5 10 19.3 0.6 0.5 323 280.5 77
3000 12.5 10.8 28.6 0.4 0.4 235 204.4 80
3500 16.7 14.5 37.8 0.4 0.4 238 207.1 82
4000 24.3 21.1 45.2 0.5 0.5 291 252.7 83
4500 32.8 28.5 52.7 0.6 0.5 336 291.8 86
5000 39.5 34.3 68.5 0.6 0.5 312 271 87
5500 44.6 38.7 84.7 0.5 0.5 284 247 86
6000 49.2 42.7 125.2 0.4 0.3 212 184.3 88
6100 52 45.2 133.2 0.4 0.3 211 183.4 88


Length Overall 41'4"
12.60 m
Beam 13' 6''
4.11 m
Dry Weight 24,518 lbs.
11,121 kg
Tested Weight 31,622 lbs.
14,343 kg
Draft 31''
78.74 cm
Deadrise/Transom 19-deg.
Bridge Clearance 14' 2''
4.32 m
Person Capacity 20
Fuel Capacity 600 gal.
2,271 L
Water Capacity 90 gal.
341 L
Total Weight 31,622 lbs.
14,343 kg

Acceleration Times & Conditions

Time to Plane 4.7 sec.
0 to 30 12.9 sec.
Load 3 persons, 3/4 fuel, full water, 50 lbs. of gear
Climate 86 deg., 68 humid, wind: 5-10 mph; seas: calm

Engine Options

Tested Engine 4 x 400-hp Mercury Verado Joystick PLT
Std. Power 4 x 300 Mercury Verado V8 DTS black engines
Opt. Power 4 x 300-hp Mercury Verado V8 DTS white engines
4 x 350-hp Mercury Verado L6 DTS black or white engines
4 x 400-hp Mercury Verado L6 DTS black or white engines
4 x 300-hp Mercury Verado V8 DTS black or white engines with Joystick Piloting
4 x 350-hp Mercury Verado L6 DTS black or white engines with Joystick Piloting
4 x 400-hp Mercury Verado L6 DTS black or white engines with Joystick Piloting

Captain's Report

Captain's Report by Capt. Martin Frobisher


The Boston Whaler 405 Conquest is 40’ long (12.19 m) with a 13’’6” (4.11 m) beam and she can be powered by up to quad 400-hp outboards.

Mission Statement

The flagship of the Boston Whaler Conquest line is designed to be able to head offshore for a day of fishing or take the family for an extended cruise with equal efficiency and capability. She has a spacious cockpit and can be equipped more for fishing or cruising to suit an owner’s needs. The helm deck lounge converts to multiple positions and belowdecks, she has a private cabin in the bow.

Major Features

  • Hull side dive or tuna door
  • Fish boxes with glycol cooling tubes
  • Patent-pending pocket door for bow stateroom
  • Head with separate shower stall
  • Hardtop with large opening skylight
  • Available outboard power up to a total of 1,600-hp

deck plan

The Boston Whaler 405 Conquest is laid out for ease of passage with unobstructed side decks and an open feel in the cockpit and on the helm deck.

Features Inspection

The Cockpit. The cockpit measures 11’3” (3.43 m) wide x 6’6” (1.98 m) fore to aft and our test boat had the summer kitchen in the stern. Under the center hatch that opens on tension hinges is an electric grill. There’s a stainless-steel rail, a drawer-style refrigerator and to port are two beverage holders. To port of the grill are the sink and two more beverage holders. On the starboard side of the summer kitchen are three drawers and the larger one to port has a dedicated retainer for a 5-gallon (19 L) bucket with a 110-volt outlet just above. If an owner prefers, the stern can be equipped with an aquarium-style live well. Twin high-gloss tables that measure 31” x 22” (78.74 cm x 55.88 cm) each can be installed in the cockpit.


At just over 11’ (3.35 m) wide, the cockpit has plenty of space for fishing fish.


Our test boat had the summer kitchen centrally positioned in the stern.


The hatch for the Kenyon grill stays open on tension hinges and is lined with a heat shield. The sink to starboard has a fold-up faucet.

wet bar

A drawer-style refrigerator is under the grill and there’s storage outboard on each side.


The drawer to port has a dedicated rack for one of the most popular accessories on any boat, a 5-gallon (19 L) bucket.


Side-by-side tables enhance the cockpit’s versatility and there’s still plenty of room to move around them.

Mechanical Equipment Access. The large hatch in the center of the cockpit deck opens on twin gas struts. Equipment accessed via the hatch includes the 15 kW Fisher Panda generator, the Seakeeper 6 gyroscopic stabilizer, and the fire-suppression system. The fuel-water separators are in reach outboard to starboard with the battery chargers just ahead. Strainers and bilge pumps are centrally positioned just ahead of the generator. Also, on the underside of the hatch are storage racks for the cockpit tables. This is an example of Boston Whaler’s Point of Use storage system. Accessories are stored as close as possible to where they are used. Showing attention to minute details, the manufacturer pads the racks with foam so the tables’ high-gloss finish doesn’t get marred when they are stored.


Access to the mechanical equipment is organized and prioritized with strainers and bilge pumps front and center.


The table storage on the underside of the equipment access hatch is an example of Boston Whaler’s Point of Use storage.

Cockpit Fishing Features. In the aft port corner of the 405 Conquest’s cockpit, we found a 19-gallon (72 L) live well with a clear hatch that opens on tension hinges. It’s aerated, lighted and has round corners and a blue finish. Just ahead in the caprail are a rod holder and a hawse pipe for stern lines that secure to the 10” (25.4 cm) cleat just below. There’s also a dedicated rack for a downrigger ball and the boat is pre-wired for the optional downriggers.

To starboard, we found the same setup plus racks for storing rods or long-handled equipment and toe rails. A first on any Conquest, the 405 Conquest has a hull side door for hauling in big fish or for hauling and retrieving divers. It opens and closes with a heavy-duty latch and hinges and there’s a swing-away stainless-steel grabrail. Bolsters are 28” (71.12 cm) off the deck and just under to port are switches for the port and starboard fish boxes and the live well. Just ahead are the fresh and raw water washdowns in that order. Crewmembers responsible for keeping the 290-quart (274 L) fish boxes full of ice will appreciate a new feature on the 405 Conquest, a low-pressure glycol recirculating system that keeps them chilled and eliminates the need for ice.


The live well in the aft port corner has all the proper design elements including rounded corners and a drain.

aft cockpit

The aft port corner shows the 405 Conquest’s dual personality with the downrigger ball rack right below the stereo speaker.


Boston Whaler even pre-wires the 405 Conquest for downriggers. This is the plug for the accessory.

dive door

The 405 is the first Conquest with a hull side door and in true Boston Whaler fashion, it’s installed on heavy-duty hardware.

grab rail

When needed, a grabrail swings into position just inboard of the hull side door to make it easier to board.

fish box

The tubes in the fish box carry glycol, which is a coolant so there’s no need to keep filling it with ice.

starboard side

Racks on the starboard side of the cockpit are better suited to long-handled gear like boat hooks than for fishing rods.

Cockpit Cruising Features. At the forward end of the cockpit are two aft-facing lounge seats. Beverage holders are in outboard cut out sections of the hardtop structure. To starboard, a footrest pulls out like a drawer and to port there’s a cooler in the seat base with two access points and a step underneath folds out. Alongside the port seat, there’s a pull-out shower. Overhead on the trailing edge of the hardtop, our test boat had the optional SureShade that extends 7’ (2.13 m) aft to provide protection from the midday sun.

cockpit lounges

With their elevated position, the cockpit lounges are the perfect spot for watching an angler fight a fish.

foot rest

Covered in nonskid strips, this footrest pulls out drawer-style to improve comfort for people seated on the starboard cockpit lounge.

seat storage

Above is a drawer that provides more storage. This would be the location for the grill if the galley replaces the seat.


The cooler in the base of the port seat has a smaller acrylic hatch or the whole seat can lift up as shown here.

fold out step

Just below the cooler, a step folds up to make it easier to get up to the port lounge.


The cockpit shower pulls out alongside the cooler, but we’re not sure about installing a stereo speaker just below.


The retractable SureShade awning that covers the whole cockpit is sure to be a popular option.

The Stern. In the aft starboard corner of the cockpit, a gate opens to provide access to the transom. Immediately inboard of the passageway are utility connections for shore power and fresh water. Across the transom, there are cupholders with a retractable shower to port. There’s space between the transom and the splash wells for a person to pass and small swim platforms on each side extend aft alongside the engines. A boarding ladder is in a compartment on the starboard platform.


The transom gate is to starboard and just below there are two drains to rid the cockpit of water.


The shore power plugs and freshwater inlet are positioned in reach of the passageway.


The 405 Conquest’s transom looks clean with single rigging tubes for each motor’s wire harness and inspection plates just ahead.

The Bow. Steps on each side of the cockpit lead to the 18” (45.72 cm)-wide passageways to the 405 Conquest’s bow. Side rails are 24” (60.96 cm) tall and there are rails on the hardtop, ensuring that the passage forward is secure. The 70” (177.80 cm) longbow sun pad is 58” (147.32 cm) wide and it has adjustable backrests plus cupholders, grabrails, and stereo speakers on each side. To port, there are USB plugs alongside the speaker. In the foredeck, there is a Lewmar windlass with a 10” (25.40 cm) cleat alongside for securing the rode. Outboard on each side are pull-up cleats and sockets for the bow shade. Alongside the windlass to starboard is a hatch that provides access to the rode locker.


Steps at the front of the cockpit lead to the 405 Conquest’s side decks.

side decks

The 24” (60.96 cm) tall rails flare out as extend off the deck, providing more width to make it easier to pass.

bow lounge

The forward sun pad is recessed into the deck and has backrests that can be adjusted to myriad positions.


Grounding tackle includes a stainless-steel anchor that stores in a dedicate chute, a Lewmar windlass and a cleat for securing the rode.


The rode locker has a light, remote control for the windlass, and a washdown, plus plenty of storage space.

The Helm Deck. Back in the cockpit, countertops fold out of the starboard lounge to provide extra serving space. The steps between the cockpit seats are 9” (22.86 cm) tall and the space between them is 28” (71.12 cm) wide. Another example of Boston Whaler’s point of use storage, the ladder for the hull side door stores in a dedicate rack in the hatch for the center locker. This compartment has access to the house batteries and chargers, the water heater and holding and water tanks. Circuit breakers for less frequently used items are on the forward bulkhead.


The hatch in the helm deck passageway opens on twin gas struts and has a rack for the hull side-door ladder.

dc breakers

All of the DC breakers in the under-deck compartment bulkhead are clearly labeled.

Convertible Dinette. The backrest for the port aft-facing seat can be easily moved to create dinette seating on the helm deck. Additionally, the table can be lowered, the forward seat in the dinette can be lowered, and the companion’s seat at the port console can be rotated aft to create an extra-long lounge. To starboard, a galley includes a single-burner Kenyon stove and a sink recessed in a Corian countertop. Beneath the countertop, there’s a bottle rack forward, storage, and a refrigerator. Our test boat also had the full-glass option with windows that filled the space between the deck and the hardtop. Glass that comes up halfway is standard. Forward, the windshield has a pair of Boston Whaler’s patented power vents. Overhead, the hardtop has a power skylight measuring 64” (162.56 cm) wide by 38” (96.52 cm) fore to aft. There’s storage for the cockpit enclosure, courtesy and spreader lights, and outrigger handles.


Flip the backrest to the aft position and adjust the angle to create dinette-style seating under the hardtop.


Step one of transforming the lounge is to lower the table.

dinette seats

In step two, the forward half of the dinette seat lowers and latches into position.


Push a button to rotate the seat at the port console to finish the transformation into an adult-sized lounge.

port helm

Notice that the front of the forward backrest can still be used as a leaning bolster.

helm galley

Across from the dinette, the starboard galley has plenty of countertop for prep space next to the single-burner stove. Underneath there’s convenient bottle storage.


The drawer-style refrigerator beneath the sink is a good choice. In our experience, these stay closed better than the units with the traditional hinged doors.

full glass

Full height windows outboard of the helm seat are part of the full glass option.


The standard boat comes with a glass that comes up halfway. Guess what Boston Whaler calls it? Half glass.

sun roof

Push a button just below in the hardtop to open the large sunroof to let in as much or as little natural light is desired.


More point-of-use storage. The cockpit enclosure stores in the soft compartment on the underside of the hardtop.

Port Console. Forward to port, the seat has space for two to sit when traveling facing forward. Ahead in the console, our test boat had a 24” (60.96 cm) Raymarine multifunction display so a companion can keep an extra eye on the course or use the screen to find a destination. In the center of the panel beneath the MFD is a locking glove box and outboard to port, a compartment houses a second joystick for docking. There are charging stations with inductive chargers and USB and auxiliary ports on top of each console.

helm seat

A pair of companions can keep the captain company during a long cruise in this doublewide seat to port.

port helm

At 24” (60.96 cm), the multifunction display in the port console is one of the largest we’ve seen.


The joystick that folds out of the port console is a great idea so that the captain can bring the boat into the dock from whichever side is more comfortable.

The Helm. To starboard, the captain travels in a single-person seat that can adjust fore and aft with the push of a button, has folding armrests and swivels. A pair of 16” (40.64 cm) MFDs come standard or a captain can upgrade to the twin 19” (48.62 cm) units on our test boat. Above, push-button-style accessory switches flanked air-conditioning vents. Below to port are the Fusion stereo control and the Mercury VesselView screens. The steering wheel is on a tilting base and alongside it to port is the remote control for the spotlight. To starboard are the ignition buttons for the motors and the trim tab switches are ahead of the digital controls, which are forward of the joystick. The latter is positioned so that the captain can reach it from the open side window when docking.

helm seat

The captain’s chair can be rotated inward so he can join the party, but it would probably be more comfortable with the bolster down.


Twin Raymarine multifunction displays monitor all of the onboard systems and provide course information.

vessel view

The Mercury VesselView screen next to the Fusion stereo eliminates the need for engine instruments.


Positioned next to the engine start-stop buttons, the trim switch panel includes built-in indicators for the tabs.


Placing some of the switches abaft the joystick keeps the dash from getting cluttered and they’re still in comfortable reach.


The Private Cabin. Between the consoles, a sliding door provides entry to the 405 Conquest’s cabin. We’re starting in the bow because one of the biggest requests that customers made for a boat in this size range was a private stateroom. To make the sliding pocket door work with the hull’s V-shape, Boston Whaler custom designed it with an articulating lower section. The company applied for a patent on the door. The bow berth is on the centerline and it measures 80” (203.2 cm) by 58” (147.32 cm). There are steps on each side to make it easier to get into bed and buttons on the port side raise the head of the berth. That could make it easier to watch the 24” (60.96 cm) TV that’s on the bulkhead along with the stereo at the foot of the berth. To starboard in the master is a cedar-lined hanging locker and to port, a closet with shelves is also finished in the aromatic softwood. Instead of drawers at the foot of the berth, the entire base opens on twin gas struts to reveal a compartment that could be large enough for a liferaft or a couple of suitcases. A Dyson vacuum cleaner is in a dedicated rack in the locker.


The cabin in the bow has 6’2” (1.88 m) of headroom.


The head of the berth can be raised electronically to make it more comfortable.


Windows on each side of the hull let in natural light.


For entertainment, the bow stateroom has a TV and stereo.

bow locker

Shelves in the bow closet all have fiddle rails to help contain the contents.

bed storage

Instead of drawers that limit storage space, a section of the berth raises on twin gas struts, offering cavernous storage.

The Head. At the foot of the berth, just inboard of the hanging locker is private entry to the 405 Conquest’s head. There’s also an entry from the dinette area. Inside the compartment has a separate shower with a rainfall head up high and a pull-up wand. There’s also a flush toilet, a vessel sink, Corian countertops, a skylight, and an opening port.


The cabin has en-suite entry to the 405 Conquest’s head.

shower stall

The shower closes off from the rest of the head so the rainfall-style head won’t soak the whole compartment.


The other half of the head includes a vessel sink and a large window with an opening port.

The Salon. Moving out into the salon/dinette area, there are overhead skylights and hull side windows that let in natural light. The table folds up to let in passengers and when it’s down, the high-gloss surface has plenty of space for a snack or a game of cards. The table can be lowered and cushions can be added to create a berth that should enough space for one adult or a couple of kids. For entertainment, there’s a stereo and a 32” (81.28 cm) TV. Behind two overhead cabinet doors are the controls for the cooling system for the fish boxes, the Spectra water maker, the TV antenna gain, and the air conditioning systems.


There’s space for folks to hang out around the table and catch a game on the TV. Instead of one large window, Boston Whaler used two small ones and each has an opening port.

dinette table

Part of the table folds up to make it easier for people to step into the wraparound lounge.

sky lights

Overhead skylights let in more natural light, which makes the cabin feel more open instead of the dark cramped feel so many boats in this size range have.

dinette filler

The table can also be lowered and cushions are added to create an extra berth. Boston Whaler says the boat can sleep six, but we don’t see two adults fitting here.


Lockers are eye level in the dinette area are so cleanly integrated into the area that they are easy to miss.

The Galley. Across from the dinette to starboard, galley has a single-burner stove, a sink and a refrigerator. Two cabinets above the sink open to reveal the microwave oven and a coffeemaker. The main distribution panel is up high with the AC and DC switches separated and labeled. A hatch in the sole opens to provide access to the optional Spectra watermaker. Just abaft the galley is a cedar-lined locker with a variety of shelves and compartments.


The compact galley has everything necessary for whipping up a continental-style breakfast.


Cabinets open to reveal the microwave oven and a coffeemaker.

waste basket

The drawer next to the galley refrigerator pulls out a wastebasket.


Located above the galley, the main distribution panel is centrally located for easy access.

The Aft Berth. Abaft the cabin stairs is an 82” by 55” (202.28 cm by 139.70 cm) mattress. The aft section raises on a power lift to access the spacious storage in the base. Overhead are racks for five fishing rods.


Boston Whaler was smart to use this type of stairs so it gives the aft berth a more open feel.

aft cabin

With 4’8” (1.42 m) of headroom above the berth, the aft cabin feels inviting rather than cramped, which is often the case.

aft cabin

Overhead racks built into the headboard have space for six offshore fishing rods.


The Numbers. The Boston Whaler 405 Conquest measured 40’ (12.19 m) long with a beam of 13’6” (4.11 m) and a draft of 2’7” (.79 m). Empty weight is listed at 24,518 lbs. (11,121 kg). With 450 gallons (1,703 L) of fuel, 90 gallons (341 L) of water, three people and test equipment on board, we had an estimated test weight of 31,622 lbs. (14,344 kg).


In a light chop and 10-mph winds, the 405 Conquest acquitted itself well, riding smoothly and maintaining her course.

Speed and Range. Our test boat was powered by quad 400-hp Mercury supercharged four-stroke outboards. Winding up the quartet of motors to 6100 rpm, we hit a top speed of 52 mph. The best cruise came at 4500 rpm where we measured 32.8 mph and burned 52.7 gph. This gave us .6 mpg and a range of 336 statute miles with 10 percent of the boat’s 600-gallon (2,271 L) fuel capacity in reserve. Minimum planing speed was 12.6 mph. At 600 rpm, the boat ran 3.6 mph and burned 2.5 gph, giving the boat a rating of 1.4 mpg. Bump up to 1000 rpm and the speed goes up to 6.0 mph with a fuel burn of 4.4 gph and the same mpg rating. In acceleration tests, the 405 Conquest planed in 4.7 seconds. She ran through 20 mph in 7.2 seconds and through 30 mph in 12.9 seconds.


With 1600-hp pushing, the Boston Whaler 405 Conquest tops 50 mph. At her most efficient, she can cover nearly 340 miles.

Handling and Docking. In maneuvers, the 405 Conquest handled well. She crisscrossed our photo boat’s wakes with ease and she showed impressive agility in tight turns for a boat of her size. When the time came to pull into the slip, the port joystick and opening side door came in handy.


For a boat of her size, the 405 Conquest has a sporty, agile feel.


With the port-side window and extra joystick, a Captain can dock from either side of the Boston Whaler 405 Conquest.


Unlike other boats that try to serve two masters and don’t really take care of either one, the Boston Whaler 405 Conquest has the features to work well whether a family wants to fish or cruise.

For fishing, she’s loaded with rod holders, comes with a live well and has fish boxes that don’t even need ice. For cruising, she has adult-sized lounges on the foredeck and on the helm deck so guests can choose between the sun and shade while they relax. Belowdecks, there’s private sleeping for two couples and our test boat had galleys with three different refrigerators.

The boat comes standard with quad 350-hp outboards and our test boat had the upgrade to quad 400s. An extra 200-hp on a 24,000-lb. (10,886 kg) the boat doesn’t seem like much but for an owner who simply must have a boat that runs faster than 50 mph, it could make the difference in a sale going through.

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