Expert Review, Technical Specifications & Market Analysis
| Feature | Specifications |
|---|---|
| Overall Length | 41' 4" |
| Beam | 13' 6" |
| Draft | 30" |
| Displacement | 22,400 lbs |
| Engines | Standard: Quad Mercury 300 V8 Verado (1,200 HP min); Optional: Quad 400 V10, Triple 600 V12 (max 1,800 HP) |
| Fuel Capacity | 620 gallons (main) plus 38 gallons (diesel generator) |
| Water Capacity | 90 gallons |
| Cabins / Heads | Private master stateroom plus mid-berth for 3 (premium innerspring mattresses); 1 enclosed head with separate shower and rain showerhead (30-gal waste capacity) |
| Max Speed | 61.5 mph (WOT with Triple Mercury 600 V12) |
| Cruise Speed | Approx. 36.0 mph @ 4,000 RPM (with Triple Mercury 600 V12 Verado) |
Source: Spec & Photos courtesy of Boston Whaler. Specs verified by Tony Smith, USCG 100 Ton Master, on August 10, 2026.
Part of the Boston Whaler Conquest series — see how owners step up through the lineup.
The 405 Conquest represents Boston Whaler's most successful attempt at building a true dual-purpose boat. The unsinkable construction is real engineering, not marketing. The foam-core hull adds weight but delivers a ride quality and structural integrity that matters when you're 50 miles offshore in building seas. The quad outboard setup provides redundancy and serviceability that inboard diesels can't match. My only concern is the complexity of the systems—there's a lot that can go wrong with quad engines, multiple refrigeration units, and integrated electronics. But the build quality is there to support it.
This boat is for the experienced owner who operates their own vessel and understands the costs involved. It's not for the first-time buyer stepping up from a 25-foot center console. You need to be comfortable with $20,000+ annual operating costs and the discipline to maintain service intervals on four outboards. It's also not for the owner who wants a pure fishing platform—the 420 Outrage is better for that. But if you want one boat that can fish the canyons on Friday and cruise the islands on Saturday, this is the most capable option in the 40-foot class.
Resale on Boston Whalers is consistently strong, and the 405 should hold 60-70% of its value over five years with normal use. That's better than most competitors. The challenge is finding used inventory—these boats don't come up often because owners tend to keep them. Maintenance costs are predictable if you stay on top of service intervals. The outboards are expensive to maintain, but they're also easier to service than inboards and you can replace them without major surgery. Budget $2,500-$3,000 per year per engine for routine maintenance and you won't be surprised..
Video courtesy of Boston Whaler.
Photos courtesy of Boston Whaler.
The 405 Conquest is Boston Whaler's flagship cabin cruiser: 41 feet 4 inches long, 13 feet 6 inches of beam, with a private master stateroom, a mid-berth sleeping three, and an enclosed head with a separate shower. It carries 620 gallons of fuel and 90 gallons of water, takes up to 20 people, and rates from 1,200 to 1,800 horsepower.
Deadrise at the transom is 19 degrees, dry weight is 22,400 pounds, and loaded weight is 30,360 pounds. This is the model for an owner who wants a real cruising interior without giving up outboard simplicity or the ability to fish. If the accommodation is not the point for you, the 420 Outrage puts a similar hull size into an open center console.
620 gallons of fuel, plus a separate 38-gallon diesel tank for the generator. Water is 90 gallons and the waste tank holds 30. Boston Whaler publishes no consumption or range figures, so any mileage claim you find is an estimate — but 620 gallons alongside a documented 36.0 mph cruise covers serious ground.
The generator tank is the detail worth noticing. Running the genset on its own diesel supply keeps it off your main tanks, which means air conditioning at anchor does not eat into the fuel you need to get home. That is cruising-boat logic rather than fishing-boat logic. For contrast, the 420 Outrage carries 700 gallons of fuel but only 60 gallons of water.
The 405 Conquest has a private master stateroom plus a mid-berth for three, and an enclosed head with a separate shower. Water capacity is 90 gallons, the largest in the current range, and the waste tank holds 30 gallons. That combination is what makes multi-night trips practical rather than theoretical.
A separate shower stall rather than a wet head is the detail that changes a week aboard, and so is the water. The 420 Outrage carries 60 gallons and the 380 Realm 55. Day capacity is 20 people, the highest Boston Whaler rates in the current line, so the boat entertains as easily as it cruises. Loaded it weighs 30,360 pounds against 22,400 pounds dry.
With triple Mercury 600 V12s the 405 Conquest has been recorded at 61.5 mph, with a cruise of 36.0 mph at 4,000 RPM. Boston Whaler publishes no speed figures itself, so treat these as engine-package results rather than factory claims.
Those are serious numbers for a 41-foot cabin boat weighing 30,360 pounds loaded, and the V12s are the reason. Torque low in the rev range is what lifts a heavy hull onto plane and keeps a cruise speed honest with fuel, water and people aboard. The rating runs 1,200 to 1,800 horsepower, so triple 600s sit near the top of it. For most owners the 36.0 mph cruise is the number that matters, because it turns a long coastal run into an afternoon.
The 405 Conquest is the bigger, more capable cruising boat; the 380 Realm is the tighter, lighter one. The 405 is 41 feet 4 inches by 13 feet 6 inches with a private master stateroom, a mid-berth for three, a separate shower, 620 gallons of fuel and 90 gallons of water. The Realm is 38 feet by 11 feet 8 inches with one cabin, one head, 445 gallons and 55.
Draft is close, 29 inches against 30, but weight is not: 17,000 pounds dry against 22,400. Capacity goes from 16 people to 20. Both run outboards and both rate to a high ceiling, 1,700 horsepower on the Realm and 1,800 on the Conquest. If your cruising is a couple plus occasional company, the Realm is enough boat. If it is a family staying aboard for a week, the Conquest is the one.
Boston Whaler rates the 405 Conquest from 1,200 to 1,800 horsepower, the same band as the 420 Outrage and the highest in the current line. That means triple or quad outboards. Triple 600 V12s have been recorded at 61.5 mph with a 36.0 mph cruise at 4,000 RPM.
The boat needs it. Dry weight is 22,400 pounds and 30,360 pounds loaded with engines, fuel, water and gear, making this the heaviest model Boston Whaler currently builds. Beyond speed, the argument for the larger packages is redundancy: on a cruising boat carrying family rather than crew, getting home on the remaining engines is worth more than any top-end figure. Deadrise at the transom is 19 degrees.
