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The 39 Rockit with 725 Ilmors and Indy drives hit 115 mph

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Old 04-16-2010, 08:45 PM
  #21
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Originally Posted by C_Spray View Post
Don't confuse torque at the crankshaft with torque at the propshaft. If the Merc 700 makes it's power at 5250, then it has 700 ft-lb at the crank. If the Ilmor makes 725 at 6300, then that's 605 ft-lb at the crank. If the Ilmor uses a 1.5 drive and the Merc a 1.25, then the Ilmor wins at the prop: 908 ft-lbs at 4,200 versus 875 ft-lb @ 4,200 rpm.

Where the Merc has a potential advantage is under acceleration. If Mercury chooses to up the boost in the mid-range, the power curve can be fattened up as much as they want.

Ain't competition grand?
this makes no since.... to me anyway..
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Old 04-16-2010, 08:57 PM
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As delivered stock - the ilmors put more power to the props than the Mercs for 2 reasons and are much lighter.

Back to the power.

Dustin Whipple himself has dynod multitudinous merc 6 and 700's and according to his dyno they do not make the factory rated power. The Merc 525 consistently makes more like 545 but the blown mercs dont.

Ilmors dont come off the dyno till they rate-its their policy.

Combine this with the Indy drives lower parasitic loss than the NXT's and the Ilmor package wins out of the box.


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Old 04-16-2010, 09:13 PM
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Curiosity:

What does the each package cost, Ilmor v. Mecury, complete with drives and headers? I like the V-10's. I just really don't know what the price difference is, just wondering.
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Old 04-16-2010, 09:17 PM
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Originally Posted by macjazzy View Post
I am definately not an expert on the Ilmore engines and I am sure someone will chime in on your statment to back me up or back you up here but,

the Ilmore's are 8.4L or 511 cu in. engines while the 700sci's are 8.2L or 502 cu in. While that is pretty close, displacement is a big contributing factor in torque production.

Both are overhead valve engines, and both are pretty close in displacement. The big difference seems to be the Merc uses a supercharger to make similar numbers to the Ilmore and the Ilmore uses 10 cyl vs. 8

So for you to say the Ilmore's are down on torque compared to the 700sci which requires a supercharger to make its power doesn't seem to make sense to me.

A naturally aspirated engine will generally make its torque at a lower rpm and maintain it longer than a super, or turbo charged one. At least that was always my understanding.

Again, could be wrong.
my opinion is the ilmors are 10 cylinders splitting 511 cu.in equaling 51.1 cu per cylinder. the merc,if it is a 502, split in 8 cylinders is 62.75 cu. if you take 2 cylinders off the ilmore,like a v-8,and keep it at 51.1 cube it comes out to 408.8 cu.in. small block size where the merc is 11 cu.in bigger per cylinder. torque is made from big bores so a smaller bore engine would be harder to make torque....... just my opinion if you understand
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Old 04-16-2010, 09:18 PM
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sorry, still a bad azz boat though....love the sound of those ilmors...... and fuel economy
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Old 04-16-2010, 09:25 PM
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sorry, still a bad azz boat though....love the sound of those ilmors...... and fuel economy
the fuel economy of my 32 skater with Ilmors and 6's is better than my 32 skater raceboat was with 2 2.5 outboards!
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Old 04-16-2010, 10:07 PM
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the fuel economy of my 32 skater with Ilmors and 6's is better than my 32 skater raceboat was with 2 2.5 outboards!
2.5's are thirsty,very thirsty
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Old 04-16-2010, 10:09 PM
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Wow!! That's a pretty sweet ride; those Ilmors sound pretty cool.
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Old 04-17-2010, 08:00 AM
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GPS is all that matters...the rest is just all hype. This boat tops does 108 tops with a high X.. Prove me wrong.....
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Old 04-17-2010, 08:12 AM
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GPS is all that matters...the rest is just all hype. This boat tops does 108 tops with a high X.. Prove me wrong.....
Sadly John from Hustler is more hype than anyone in the boat business (Reggie must have passed on some tips to him last year). On the other Hustler thread he was very proud of "the dividends" of his nutty ad campaign and how his "crews are the only ones in the boat business working 40 hour weeks." Yet when I specifically asked how many of the 39 Rockits he has built/sold over the last 2 years (since they are the best, fastest boat out there right now) all I got was silence much like this thread when the GPS was requested.
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