MerCruiser
496 MAG HO (425-hp)

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OVERVIEW
BOATS TESTED
SPECS
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FEEDBACK

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	V8
Aspiration	Normal
Displacement	8.1 L /496 CID
Bore & Stroke	4.25 x 4.38
Fuel System	Sequential Multi-Point Electronic Fuel Injection
Base Engine Weight	1199 lbs.
Length/Width/Height	35 x 33 x 24
Max RPM@WOT	4600-5000
Warranty	3-year

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.

Boats Tested with this Engine
Cobalt 220
Cobalt 24 SX (Not a Current Model)
Baja 242 Islander
Baja 25 Outlaw (Not in Production)
Chris-Craft Corsair 25 (2002)
Doral 245 Phazar (Not in Production)
Baja 26 Outlaw (2007-)
Baja 275 Performance (Not in Production)
Baja 277 Islander
Baja 278 Performance
Fountain 27 Fever
Cobalt 282
Monterey 268 Sport Cruiser
Baja 30 Outlaw
Baja 302 Performance (Not in Production)
Cigarette 30 Mystique
Baja 335 Performance
Baja 33 Outlaw (Not in Production)
Eliminator 33 Daytona
Baja 35 Outlaw (2006)
Cobalt 343
Formula 350 Sun Sport
Baja 38 Special (Not in Production)
Fountain 38 Express Cruiser
Baja 405 (2006-)
Four Winns 47 Excalibur (Not in Production)

MerCruiser 496 MAG HO (425-hp)
Propshaft HP	425-hp
Max RPM@WOT	4600-5000
Dry Weight	1199 lbs.
Length/Width/Height(in)	35 x 33 x 24
Displacement (liters/cu.in)	8.1 L /496 CID
Aspiration	Normal
Cylinders/Configuration	V8
Bore & Stroke	4.25 x 4.38
Alternator Output Rating	65 amp
Shaft Length	~
Fuel Type	87 Octane
Fuel System	Sequential Multi-Point Electronic Fuel Injection
Exhaust System	Tuned Runner Exhaust Manifolds w/316 SS jt elbows
Ignition System	Distibutorless Ignition with Knock Control
Cooling System	Closed Cooling, Brass Sea Water Pump
Electronic Engine Display	Yes


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

Have you used this engine? Give us your feedback/comments.

r. blake	8/9/2009 5:44:18 PM
i have a 496 ho in my 25 Outlaw I keep getting the over heat alarm. but the gauge only shows it getting to 175 F and my lower gear lube shows good can anyone help me on what else it might be. I took my lower hose of my heat exchanger and there was not any fuild coming out, is there supposed to be liquid in the heat exchanger when the engine is off. Please help

J. Wells	7/24/2009 8:44:54 PM
Just blew 496 Mag HO engine. Bought used BAJA Outlaw 2006 with an extended warranty. 70 seconds of over remming (550 hours on boat). Here is what happened, one bolt on the end cap of one of the pistons came off

e. rob	1/19/2009 6:06:18 PM
I have the same problem with the heat exchanger but i seem to be loosing antifreeze when the engine cools any ideas, Its not in the oil

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

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Key Features

MerCruiser 496 MAG HO (425-hp)