Mercury Mercruiser Engines

Marine Inboard 8.1 Horizon - 370 hp

The Horizon 8.1 offers a four-year factory warranty when installed by one of our many Installation Quality certified boat manufacturers. Producing 370 horsepower, it has become one of most popular choices for powering larger cruisers and houseboats. Fitted with our most sophisticated Multiport Injection (MPI) and ignition system, the 8.1 Horizon is the pinnacle of gas inboards. Like all MerCruiser inboards, the Horizon 8.1 is available with a large variety of popular transmissions to fit virtually any application. Digital Throttle & Shift (DTS) is available and is mated to a direct-acting electric shift transmission. DTS eliminates cable maintenance and provides consistent and precise throttle and shift control, and never requires any adjustment. DTS can automatically synchronize multiple engines, provides shift protection and provides SmartStart digital starting. DTS also features Transmission Guardian to automatically protect against damage from overheating or low fluid levels.

   Mercury Mercruiser Marine Engines Inboard 8.1 Horizon - 370 hp


  • PCM 555 sequential fuel injection and high energy distributorless ignition system ensure reliable starts and outstanding performance, year after year
  • Exclusive Engine Guardian protection senses potential problems and virtually eliminates the chance for engine damage due to overheating, low oil pressure, or low drive lube
  • Cartridge-type water-separating fuel filter helps protect fuel system and engine against damage
  • Industry-exclusive 3-year limited corrosion failure warranty
  • High-mount starter and aluminum oil pan are protected from salt water for years of reliable operation
  • Cast iron exhaust manifolds and 316 stainless steel elbows better resist high temperature and corrosion and improve exhaust flow for more power
  • Brass sea water pump housing improves life and better resists damage from running dry


  • Long individual runner intake manifold design provides optimum torque and horsepower for demanding marine applications
  • Tuned runner exhaust manifold lowers exhaust backpressure for best torque and power
  • Sequential fuel and spark control maximizes performance from every engine cylinder
  • High energy distributorless ignition with knock control maximizes power and protects against low quality fuels
  • Low restriction flame arrestor for added horsepower and torque
  • Variety of available high quality hydraulic transmissions and gear ratios allow boat manufacturers to precisely match hull characteristics and boat weight to optimize performance


  • 3-year/300 hour maintenance interval on many periodic service items saves time and money
  • Convenient remote oil filter location makes oil changes cleaner and makes periodic service simple and less work
  • Color-coded service points makes checking fluid levels simple and straightforward
  • Operates on easy to find, less expensive 87 octane fuel
  • Long-life anti-freeze only requires replacement every 5 years
  • Single point air-actuated water drain system standard
  • Dual dipsticks for easy service access


  • Optional DTS provides unparalleled control system technology to insure years of maintenance-free and reliable shifts and silky-smooth throttle control. Automatic engine synchronization, electric shift control and running start protection make this option a must for larger yachts
  • Exclusive Transmission Guardian monitors temperature and clutch pack pressure and protects transmission from damage due to overheating or clutch slippage due to low hydraulic fluid pressure (DTS Only)
  • Large 65 Amp alternator provides plenty of power for popular onboard electronics
  • 8.1S and 8.1 HO engines are designed to display engine information on your choice of analog or SmartCraft digitally-driven gages and displays

Power 370HP (272 kW)
Full Throttle Range 4200 - 4600 RPM
Displacement 496 CID (8.1L)
Engine Type V8
Bore & Stroke 4.25" X 4.38" (108mm X 111mm)
Compression Ratio 9.1:1
Fuel Requirement 87 Octane (R+M)/2
Engine Control System PCM 555 with SmartCraft CAN Capability - DTS Optional
Fuel Delivery System Gen III Cool Fuel
Fuel Injection System Sequential Multi-Point Electronic Fuel Injection
Induction System 2-pieceLong Runner intake with 75mm Throttle Body (80mm w/DTS)
Ignition System Distributorless Ignition w/Knock Control and Platinum Spark Plugs
Charging System 65 Amp/917 Watt Alternator
Water Drain System Single Point Air-Actuated
Exhaust System Long Runner Cast iron Manifolds with 316 Stainless Steel Tubular Dry Joint Elbows
Cooling System Closed Cooling, Long Life 5-Year Anti-Freeze, Brass Sea Water Pump
Accessory Drive System Serpentine Belt, Stainless Steel Spring Automatic Tensioner
Recommended Engine Oil Mercury MerCruiser Full-Synthetic Engine Oil, 20W-40, NMMC FC-W rated
Engine Guardian System Low Oil Pressure, High Coolant Temperature, High Exhaust Manifold Temperature, Low Sea Water Pressure, Low Voltage, Over-rev control, Knock Control, Transmission Temperature, Low Transmission Fluid Pressure (DTS Only)
ZF 63A (Available w/DTS) 1.5, 2.0, 2.5,2.7:1
ZF 80 A (Available w/DTS) 2.85:1
ZF 63 IV (Available w/DTS) 1.5, 2.0, 2.5:1
Dimensions (LxWxH) in 47x 33 x 24
Dimensions (LxWxH) mm 1194 x 838 x 610
Weight (lbs./kg) 1130/513
Digital Throttle & Shift Standard

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Bullock Marine offers new & used powerboats as well as performance boat accessories: skater, fountain, eliminator, Mercruiser Mercury Marine (competition - racers & performance propellers, Zero Effort Controls™, K-Plane™ high performance trim tabs, Mercury Racing Trim Indicators™, high performance engines, competition drive, etc.) cigarette boat, welcraft, scarab, donzi boats, catamaran raceboat, high speed twin hull, etc. Bullock Marine is an authorized dealer for Douglas Marine Skater Powerboat, Regy Fountain powerboat & sport boat, Eliminator powerboat & sport boat, and Mercury Mercruiser marine engines, Drive & accessories. Mercury Mercruiser HP 1075 SCi 1075 HP marine engines racing boats Mercury Marine HP 575 SCi 575 HP Sterndrives performance boat Mercruiser HP 525 EFI 525 HP race boat engine for sale powerboats Mercury Mercruiser HP 500 EFI 500 HP stern drives power boat Mercury Marine Scorpion 377 377 HP marine engines high performance boats Mercruiser 496 MAG High Output 425 HP Sterndrives sport boat Mercury Mercruiser 496 MAG 375 HP race boat engine for sale powerboat Mercury Marine MX 6.2 MPI Horizon 320 HP stern drives performance boats Mercruiser MX 6.2 MPI 320 HP marine engines power boats Mercury Mercruiser 350 MAG MPI Horizon 300 HP Sterndrives engines Mercury Marine 350 MAG MPI 300 HP race boat engine for sale mercruiser Mercury Drive Dry-Sump Six drive racing mercruiser powerboats mercury Bravo One XR Sport Master sport boat drives sport boat V SSM drive mercury race power boats III-A SSM drives mercury mercruiser racing boats Bravo One XR drive powerboat Bravo X Diesel mercruiser drives sport boats Bravo XR mercury drive for sale power boats Bravo X drives mercruiser boats Bravo mercury drive sales pleasure Alpha drive mercruiser boat

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