The 39 Rockit with 725 Ilmors and Indy drives hit 115 mph
04-15-2010, 07:47 PM
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04-16-2010, 06:07 AM
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I've seen the video on the 700 boat and now 725 Ilmor boat.,.both beautiful boat...LETS SEE THE GPS FOR VERIFICATION
04-16-2010, 06:30 AM
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That's my understanding. The Indy transmission and drive are both dry sump and apparently very low drag, so things are probably pretty even at the prop.
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04-16-2010, 07:24 AM
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The only problem with Ilmore engines that they do not have the same torque as mercs or any other engine in the 700class.
Torque is what pushes the boat.
Torque is what pushes the boat.
04-16-2010, 09:57 AM
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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.
04-16-2010, 10:17 AM
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04-16-2010, 11:03 AM
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Don't confuse torque at the crankshaft with torque at the propshaft. If the Merc 700 makes it's power at 5200, then it has 707 ft-lb at the crank. If the Ilmor makes 725 at 6300, then that's 604 ft-lb at the crank. If the Ilmor uses a 1.5 drive and the Merc a 1.24, then the Ilmor wins at the prop: 906 ft-lbs at 4,200 versus 877 ft-lb @ 4,194 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?
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?
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Last edited by C_Spray; 04-17-2010 at 01:10 PM.
04-16-2010, 02:47 PM
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