For you all that have 496 MAG/496 MAG HO engines, what kind of oil pressures do you see? I've been running Mercury's 25W-40, and I see about 45-50 lbs at startup, 42-45 at cruise, and ~40 or just under at WOT. When I throttle down to idle, pressure drops to just above 20lbs, but a blip of throttle shows it jumping right back up to 40 lbs. Anybody else seen similar behavior? Anyone think I need a remote oil cooler? Thanks!

I don't know about the 496's, but it sounds almost identical to my 502.

That sounds just like my 496HO. It did seem to be a little better with Mobil 1 15-50. I have also noticed that the oil gets a little diluted with fuel after 5 hours of use and the transom turn black after a hour of use. As of now I wish I would of purchased the 500 EFI.

This is right out of the Mercruiser manual...

Model: 496 MAG Sterndrive engine specs
Engine
Propshaft Power 375 hp (280 kW)
Displacement 496 cid (8.1L)
Engine Type / Rotation V8 Gen+ / LH
Bore x Stroke 4.25 in. x 4.38 in. (108.0 mm x 111.3 mm)
Compression Ratio 9.1:1
Compression Pressure Minimum 100 psi (690 kPa)
Oil Pressure @ 2000 RPM Minimum 30 psi (207 kPa)
Oil Pressure @ Idle RPM Minimum 15 psi (103 kPa)
Valve Adjustment / Lifter See Service Manual #30 / Roller
Thermostat 160° F (71° C)
Ignition
Type of Ignition System Distributorless Ignition
Firing Order 1-8-7-2-6-5-4-3
Spark Plug Type Original: Denso TJ14R-P15
Spark Plug Gap .060 in. (1.5 mm)
Initial Ignition Timing N/A
Electrical
Alternator 72 Cold Operating Amps, 65 Hot Operating Amps
Battery Required Minimum 650 cca or 825 mca (150 Ah), 12V Negative (–) Ground
Fuel
Type of Fuel System Multi-Port Fuel Injection with Electric Fuel Pump
Fuel Required Minimum 87 Octane [R+M/2] / (90 RON)
Fuel Pressure Boost Pump 7 psi (48 kPa), EFI Pump 43 psi (296 kPa)
RPM
Idle RPM 650 RPM in Neutral Gear
Full Throttle RPM 4400-4800 RPM
Date Code Location Stamped On Machined Cylinder Block Boss On Rear Starboard Side
Fluid Capacities
Oil Change with Filter Approx. 9 U.S. Quarts (8.5 L)
Closed Cooling System 19 U.S. Quarts (18.0 L)
Sterndrive Gear Lube Same as before
MIE Transmission N/A
Torque Specifications
Exhaust Manifold 26 lb-ft (35 Nm)
Exhaust Elbow 15 lb-ft (20 Nm)
Intake Manifold
106 lb-in. (12 Nm)
Cylinder Head See Service Manual #30 for procedure
Flywheel 74 lb-ft (100 Nm)
Flywheel Coupler/Drive Plate 35 lb-ft (48 Nm).


Model: 496 MAG HO Sterndrive engine specs
Engine
Propshaft Power 425 hp (317 kW)
Displacement 496 cid (8.1L)
Engine Type / Rotation V8 Gen+ / LH
Bore x Stroke 4.25 in. x 4.38 in. (108.0 mm x 111.3 mm)
Compression Ratio 9.1:1
Compression Pressure Minimum 100 psi (690 kPa)
Oil Pressure @ 2000 RPM Minimum 30 psi (207 kPa)
Oil Pressure @ Idle RPM Minimum 15 psi (103 kPa)
Valve Adjustment / Lifter See Service Manual #30 / Roller
Thermostat 160° F (71° C)
Ignition
Type of Ignition System Distributorless Ignition
Firing Order 1-8-7-2-6-5-4-3
Spark Plug Type Original: Denso TJ14R-P15
Spark Plug Gap .060 in. (1.5 mm)
Initial Ignition Timing N/A
Electrical
Alternator 72 Cold Operating Amps, 65 Hot Operating Amps
Battery Required Minimum 650 cca or 825 mca (150 Ah), 12V Negative (–) Ground
Fuel
Type of Fuel System Multi-Port Fuel Injection with Electric Fuel Pump
Fuel Required Minimum 87 Octane [R+M/2] / (90 RON)
Fuel Pressure Boost Pump 7 psi (48 kPa), EFI Pump 43 psi (296 kPa)
RPM
Idle RPM 650 RPM in Neutral Gear
Full Throttle RPM 4600-5000 RPM
Date Code Location Stamped On Machined Cylinder Block Boss On Rear Starboard Side
Fluid Capacities
Oil Change with Filter Approx. 9 U.S. Quarts (8.5 L)
Closed Cooling System 19 U.S. Quarts (18.0 L)
Sterndrive Gear Lube Same as before
MIE Transmission N/A
Torque Specifications
Exhaust Manifold 26 lb-ft (35 Nm)
Exhaust Elbow 15 lb-ft (20 Nm)
Intake Manifold
106 lb-in. (12 Nm)
Cylinder Head See Service Manual #30 for procedure
Flywheel 74 lb-ft (100 Nm)
Flywheel Coupler/Drive Plate 35 lb-ft (48 Nm)

RacingFan,

Mine behaves identically to yours. About 48-50 at cold startup, 45 at cruise all the way to WOT and about 25 hot idle.

Thanks for the responses y'all! I feel alot more comfortable now with the oil pressures I've been seeing all season.

Daze,
What oil do you run in your 496HO? I've never run anything but Merc's 25W-40; been thinking about straight weight, but it's about to get alot cooler up here with fall coming

I ran Merc's 25W-40 for the first 120 hours, which was like 7 oil changes. I just recently switched to straight weight 40 oil two oil changes ago, purely for cost savings. I've noticed no difference whatsoever. Pressure is the same, temps seem to be unaffected and the color is the same at different points in time and not a drop used. I've never lost a drop of oil after the first 10-15 hours.

Merc recommends straight weight 40 second to their own 25W-40...I think it's purely about the money.

I think it's about the money too...at ~ $3.25/quart that I'm paying for Merc's 25W-40, I'm already more than halfway to what it costs for synthetic! Most tech articles I've read in the last year recommend straight weight 40 over multi-viscosity anyway....I think I'll make the switch!