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496 MAG HO (425-hp)

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496 MAG HO (425-hp) 496 MAG HO (425-hp)
The new high-tech 496 MAG HO (high-output version) represents the next generation of powerful, smart, virtually maintenance-free engines. The PCM 555 microprocessor is built right in, so you can take advantage of everything SmartCraft™ has to offer in the way of increased performance and convenience. And by incorporating Horizon™ engine technology, it offers a 3-year extended maintenance interval (except for periodic fluid-level checks and seasonal oil and filter changes).

Fast Facts
Propshaft HP 425-hp
Configuration V-8
Displacement 8.1 L /496 CID
Bore & Stroke 4.25 x 4.38 in. (108mm x 111mm)
Fuel System Sequential Multi-Point Electronic Fuel Injection
Base Engine Weight 1,199 lbs.
Length/Width/Height 35x33x24 in.
Max RPM@WOT 4600 - 5000 rpm
Warranty 3 years

Key Features

  • Compatible Drives: Bravo One X, XR, Bravo Two X, Bravo Three X, XR
  • Distributorless ignition system that improves timing accuracy and eliminates mechanical timing adjustments.
  • Closed cooling with 5-year coolant.
  • Redesigned exhaust system with aluminum manifolds and stainless steel elbows that is 65 percent lighter and more corrosion-resistant.
  • Dry-joint technology that reduces the potential for water leakage in exhaust components and improves corrosion resistance in the exhaust system.
  • Innovative new single-point air-actuated raw water drain system, which enables boaters to extend their boating season into the cold months.
  • Bronze seawater pump for longer life and more durability.
  • Billet steel special profile camshaft with roller followers provide quiet operation and increased performance.
  • Platinum-tipped spark plugs to ensure long life and trouble-free starts.
MerCruiser 496 MAG HO (425-hp)
Base Price N/A Max RPM@WOT 4600 - 5000 rpm
Propshaft HP 425-hp Alternator Output Rating 65 amp / 917 Watt Alternator
Dry Weight 1,199 lbs. Fuel Type Gasoline
Length/Width/Height(in) 35x33x24 in. Fuel System Sequential Multi-Point Electronic Fuel Injection
Displacement (liters/cu.in) 8.1 L /496 CID Ignition System Distributorless Ignition
Cylinders/Configuration V-8 Cooling System Closed Cooling, Brass Sea Water Pump
Bore & Stroke 4.25 x 4.38 in. (108mm x 111mm) Exhaust System Tuned Runner Exhaust Manifolds w/316 SS jt elbows
Shaft Length Electronic Engine Display
Aspiration    
Engine Image

MerCruiser 496 MAG HO (425-hp)

  • MerCruiser water-cooled and insulated fuel system, which eliminates the need for a return line to the fuel tank, helps keep fuel temperatures down and greatly reduces the potential for vapor lock

  • d,katz 6/13/2008 8:23:34 AM
    I had this engine installed on a cobalt 252 last season. Had to use a harness adaptor. When the engine is off, the battery drains in under a week if not used. Any suggestions on why this might be or if it is not wired properly (ignition switch, etc.). My prior engine set up did not do this. Use new optima battery and for now have to use a guest off switch to turn everything off to protect my battery from this discharge condition.Thanks (katzlaw@msn.com) Dan
    d,katz 6/13/2008 8:20:29 AM
    I had this engine installed on a cobalt 242 last season. Had to use a harness adaptor. When the engine is off, the battery drains in under a week if not used. Any suggestions on why this might be or if it is not wired properly (ignition switch, etc.). My prior engine set up did not do this. Use new optima battery and for now have to use a guest off switch to turn everything off to protect my battery from this discharge condition.Thanks (katzlaw@msn.com) Dan
    m,jansen 5/3/2008 1:07:51 PM
    Any history of the heat exchangers on the 496 mag leaking? Lakewater got into mine and diluted the coolant. Now I need a new block. Less than 3 years old and only 126 hours. Mercruiser says there is not enough water in the exchanger to crack the block. Formulaguard says I did not winterize it properly whick was the same procedure the previous two years. mjansen@jansenchevrolet.com
    G,Rasmussen 4/16/2008 10:50:43 AM
    I have owned a 496HO since they first came out 2003-04. Besides toasting two stock Bravo Drives under warranty, and a coupler, the engine has been bullet proof. I have 500 hrs on it, and it still runs like it was new. Mercury finally replaced the drive with a XR drive and I have no problems with the drive since then. Of course, since my warranty has expired I have eased up a bit on my takeoff and extended full throttle usage.Razz