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What's your cruise RPM?

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Old 02-09-2007, 08:06 PM
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3500 rpm = 70 mph. 17 X 31 4 blade prop, 1.33 drive ratio.


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Old 02-09-2007, 08:20 PM
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My 29 fountain HP 500 cruised at 4000rpm 54 mph. Max rpms is 5300.

My 38 Fountain CC with triple 275 Verado's cruises nice at 4500rpm at 52mph. Max rpms is 6300.
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Old 02-09-2007, 08:20 PM
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I run around 3500 to 3800 @ 65-68mph
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Old 02-09-2007, 08:45 PM
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I've seen better. Drove Bill Taylors 42 Fountain Poker Runs America boat on Lake Michigan in summer 05, and seen just under 4000 rpm in the mid 80's
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Old 02-09-2007, 08:53 PM
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My Scarab with trips & 17x31 4 blades 4000 is 67-70 (gps). My GTX with 17.5 x 34 5 blades 4000 is 98-102 (gps).
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Old 02-10-2007, 09:29 AM
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General rule is 75% of WOT is cruise speed.

95% for diesel boats.
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Old 02-10-2007, 09:35 AM
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According to Boattest.com on most stock motors your peek fuel economy is at 2800, but I know it's hard to go that slow.
As far as how hard it is on your motors 3000 vs 4000, my Merc manual says that marine engines were made to run at WOT for extended periods of time??? JB
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Old 02-10-2007, 09:43 AM
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32-3600 depending who's on the boat and what the sea conditions are. The boat like 3600 the best which is 58 mph.

As far as fuel efficiency... even if the motor is fuel efficient at 2800 the hull may not be so you actually burn more fuel cause you're running a lot slower. I don't know the science of the deal but when you drive the boat enough you just "know" what the best cruise speed is for efficiency, comfort, speed etc. If you burn 30 GPH and it takes you 2 hours to get there it's the same as burning 60 gph when it only takes an hour...

In my case I need to get the boat out of the water and STAY out of boost for good range.

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Old 02-10-2007, 10:16 AM
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4400 rpms, 92 mph
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Old 02-10-2007, 10:35 AM
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Based on 75% of Wot (WOT/cruiseRPM/CruiseMPH)
These are actual numbers, I have recorded lots of data on all of my past and current boats.

98 OuterLimits, T840hp, 1.36gears, (5800/4350/85mph)
Magnum race boat, T 650hp, 1.50 gears, (7500/5500/78mph)
Stingray 230LX, 350magMPI, 150 gear, (4500/3375/44mph)
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