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a friend asked me what I guess the potential horsepower could be on the new 300R 4.6L V8 outboard motor.

I said there's no guessing, we can calculate the potential horsepower

currently the 400R motor generates 400HP from a supercharged 2.6L engine block

We first need to get the multiplier to determine the HP / Liter (in other words, what is the horsepower per liter)

That formula is

2.6 * M = 400 HP


calculating for M, we get

M = 400 / 2.6

M = 153.846

or in words, MercuryRacing is capable of building 153 horsepower for every supercharged liter of powerhead

so what is the 300R potential for producing maximum supercharged horsepower?

let's calculate again


4.6 * M = X where X is the maximum supercharged horsepower we can squeeze out of the 4.6L powerplant

we already calculated the M (multiplier) that 153, or 153.846 to be exact

thus

4.6 * 153.846 = 707 horsepower

in words it means, if we apply the same supercharging know how of MercuryMarine to their new 4.6L platform, we have a potential horsepower maximum capacity of 707 horsepower

let's detune that a little to make a race engine with 0 warranty of say 650 HP

detune that again to add warranty and we're down to a motor between 550HP and 650 HP

so thats the answer, the 300R when supercharged has the potential to develop 550~650 HP






.

I want to know if the lowers will be able to handle the power at 500+.

It can if its a clean slate design like the outboards. Don't forget the turbo motors start at 1100 HP.

Mercury is still using very old car based designs for most of the line. Ski boat power plant manufactures at least go with somewhat newer designs to start with.

You can get this 550HP motor with a 5 year warranty,,,,,,,,,,,, couple of these in a 28-30 sport boat with a outdrive that wouldn't blow apart would be a nice little package. And if you have been around ski/wake boats those things get beat and are loaded down big time.

xs-550 ? PCM Engines

But the new 4.6L OB do raise the bar in what could be without a doubt.

The lowers look strangely similar to Bravos. Do they use bravo gears?

And then there's the Turbo factor..... 4.6=580 if using 1100 figures.... 870ish with 1650 #'s. Would like to see merc develop an inboard exhausting turbo setup for this 60 degree V8. I think the bottom line is they don't have to make huge power if they can keep the weight down. Can you imagine a couple tiny snails nestled in the valley of those V8's making way more torque at a few hundred pounds less than a 7 marine.

The million dollar question.
When are they upgrading the lowers to 5 inch gears?