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How fast should I really be?

Old 06-26-2020, 03:32 PM
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Default How fast should I really be?

I have an American offshore 3100. Running twin 454 with m1 pro chargers running 5-6 pounds of boost. Bravo outdrives 1.36 ratio and 30 pitch props. All I can really get it to is 4800 rpms and around 80-82 GPS. Doesn’t really seem right to me. Anyone have any opinions?
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Old 06-26-2020, 10:22 PM
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I know those AO weren’t all that fast, stock lowers?
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Old 06-26-2020, 10:44 PM
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Sounds like you need less prop. Using 82 you get 18% slip with your numbers. That should be much lower for a cat also. I’d try a set of 28s and try to get the RPMs up to around 5200 or so
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Old 06-27-2020, 07:25 AM
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I have ridden on a 3100 w/ 496MAG HOs and we got it up to low 90s. If your engines are healthy something is wrong with the setup. I agree w/ both of the above posts (try different props or lowers) but first I’d call an expert on the boat about setup. Send Art DiNick on this forum a message. He was very helpful w/ my old NSX 2600.
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Old 06-27-2020, 07:55 AM
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something is off..

I have a 2003 Awesome Thundercat (same hull) with 525's and ITS boxes .
1.36 ratio stock length sportmaster lowers.
on A 100 degree day I spin stock Bravo 30's 5450 RPM for 98.1 MPH and labbed 32's 5200 RPM @ 98.6 MPH


Is the hull full of water ? MINE has 7 bilge pumps as every compartment is sealed...

How deep are the drives ?
My propshafts are 3/4" below the bottom which IS deep for this hull....


Doug

Last edited by Boatally Insane; 06-27-2020 at 08:21 AM.
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Old 06-28-2020, 05:43 PM
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Yes stock lowers. I talked to art w while back I need to check how far my prop shaft is below the hull first and maybe try some different props. One motor is brand new and the other is healthy as well. As far as the bildhe I believe I have only 1 but I checked all compartments and there is no water. Boats never see rain and is dry as a bone inside. If I’m too low I may have to invest in some shorties.

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Old 06-29-2020, 01:13 PM
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WE built a 31 with 650 HP bravo XRs 1.50 ratio on Stellings boxes about 2 inches above and runs 115 to 120 with 34 Maximus props.
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