Specifications
SmartCraft: Yes
HP: 425
kW: 317
Displacement Liter/CID: 8.1/496
Cylinder/Configuration: V-8
Bore & Stroke (in): 4.25 x 4.38
Bore & Stroke (mm): 108 x 111
Compression Ratio: 9.1:1
Fuel System: MPI
Full Throttle RPM Range: 4600-5000
Ignition System: PCM 555 Distributorless

Where did you hear 5400 RPMs? The above specs are from Mercs website. I'm repowering with a 496HO. I was thinking I was going to have to buy a new prop too. I was running a 26 Bravo 1 at 5000 rpms with 385 HP. I think the extra 40 HP is going to bump me up to a 28P. If I can turn 5400 with this motor I probably won't need a new prop.

Dave M.

Stock rev-limiter is set at 5200 - 5250 rpm. You won't get to 5400 without a re-program. Whipple's stage one kit does it (5450 rpm) and you can still run 87 octane. Their stage two requires 91 octane but has a better power output.

Bounced Check,

Thanks for the update on the rev limiter on the HO.

Also, I talked to Ray @ Raylar and he says the throttle body is the same on the HO vs. the regular mag and that is was only 7x mm ( I think he said 75mm). So although there is a different pn# for the throttle body opening between the MAG and MAG HO its really the same part. GM has been known to do this with its car lineup so it doesn't really come as a big surprise.

Back to the throttle body opening. Is it really that small of an opening? Hell, the new V8 in the Vettes have a 90mm opening and that's a 6.0 SBC. Seems Like Merc is really holding back on the potential with this motor. I was watching a boating program on tv where they visited the GM plant making the 8.1 blocks. The bore to bore accuracy was pretty amazing. To illustrate blew up the thickness of a human hair so that it was 12inches across. Then they drew a tiny little circle inside the human hair indicating the accuracy tolerances.

In summary it seems that the 8.1 MAG does have some strong aftermarket potential. But it remains to be seen if, at the end of the day, this motor can be built up to be as good or reliable as the mighty Blue 525 merc efi.

I for one hope the MAG can deliver.

Part of the HO upgrade also includes a stronger drive. You would have gotten the Bravo One X drive instead of the standard Bravo One if you had opted for the HO upgrade.

Just to put some facts in the stew. We just finished overseeing the installation of one of our BP103 kits on a bone stock 27 Ultra @ Absolute Marine in Lake Havasu, Arizona, Thursday and Friday. Boat was tested Wednesday at 0 t o plane time, 20-40 mph and 40-60 mph acceleration times and top speed mph. Prop was a labbed 24P 4 blade Bravo Conditions 70-75 degrees, very light wind chop and obviously fresh "cold" water. Boat results were taken with Garmin GPS, and stop watch. This boat is a big heavy 27 footer and has two extra monster 8D batteries alongside the engine to help run the 5000 watt sound system!!, 140 gallons of 89 octane fuel two people and about 50 lbs of gear. It's equipped with a Bravo X drive upgrade to Bravo XR specs and runs the stock Mercury exhaust manifolds with a drop elbow and out the transom. The boat before install ran 0 to plane 15 seconds ( not good) and top speed of 66.3 miles per hour honest GPS runs up and down wind average, no water current. Brought the boat to Aaron' s slick shop, they pulled the motor out of the boat ran a compression and leak down test on the motor, 155 to 160 lbs each hole with about 12% average leak downs on a 85 hour motor.
They removed the accessories, engine wiring harness and ECM, pulled the manifold, heads and camshaft and cleaned the surface of the block and checked for any visable piston , cylinder or ring dmage or obvious problems. None found. They degreed in the new cam, installed the new BigPower aluminum heads on our special Cometic head gaskets, installed the stainless roller rockers with our special AFN no adjustment locking nut and valves were set and ready to go. They installed the new Raylar "CoolGap" intake manifold, the stock throttle body, fuel rails, injectors, idle air motor, MAP and other stock sensors.
We then installed our special fuel pressure adjustment bypass hose on the cool fuel system, installed all of the rest of the stock Mercury 496 brackets, accessories, bottles, hoses and what not. We then did our special modification to the stock Mercury exhaust manifolds and risers , filled all the fluids and installed the motor back in the boat.
Hooked up all electrical, fuel and water lines, re-adjusted the fuel pressure setting and turned on the fresh water flush kit. The owner hit the key and she roard to life on the first crank and purred like a kitten! Check everything for leaks or problems, found a few hose clamps to loose, tightned and we were ready for Saturday test. Saturday was an awesome day at Lake Havasu, Arizona, clear light wind 75 degrees and an almost empty
lake! Launched at the State Park ramp two blocks from Aaron's shop and again check for leaks, drips or errors, none found! Darrell fired her up we idled out of the ramp area and made the first 0 to plane test. 7 seconds!! Less than half Wednesdays base test. Tried it three more times same results! Thats with a 26P stock Bravo 4 blade prop. We then ran all of the acceleration tests, same results, less than half the time to same speeds. The "cou de gra" was about 6 peddle to the metal top speed runs with the motor roaring like a Lion for about one full hour. Average new top speed 76.6 miles per hour and we were htting the rev-limiter at 5200 rpms on each run! They will try and run the boat Monday with a labbed 28P Bravo 4 blade. Aaron and I feel 80 mph will be about a given! at 5000rpms and yes we had four people abord for the retest not two. Over 10mph increase on the limiter, acceleration times cut by less than half. I think this will just about say all that needs to be said about the 525Hp Raylar equipped 496 engine running stock exhaust and a totally untouched 496 ECM!! Gentlemen. Its nice what an honest 100+ horsepower and gobs of torque will do for a 496 engine. This may make it hard for some boaters to step up for 20K plus more HP525's in the future. The future of the Raylar 496 is awesome for OSO'ers who have these wonderful motors. Gentlemen, I will take your Qustions! The Bull**** stops, when the Green light drops!

Regards, Ray @ Raylar

Way to go Ray! Congratulations, those are some serious results.

Brian

bn imagine doing this to your 31 sonic !!

863379A06 shows as a NLA part.. If it is the same as the Mag, that would explain it....

First post here on OSO.
My boat was the most recent Raylar project and the latest results from Ray has posted were from today.
We spun a 28 blue loaner prop off the shelf and top speed was 79.8Gps & 79.4 Gps @ 5000rpms.The overall results for this project were awesome.Cut the time to plane in 1/2 and gained 13-14mph.What else is there to ask for.Raylar has delivered everything promised.Thanks Ray & Larry!

Impressive results Ray