27' prop ?
03-26-2019 | 10:33 AM
#1
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27' prop ?
Ok I'm a newbie. I have a 27 fountain currently running a 26lh 4blade hydro 5200 78mph. For more top end speed what would you boys suggest. I have a 3blade 27 mirage on way. Dyno sheets 690hp at 5400, 670 ft tq at 5100. They meet at 5300
03-26-2019 | 01:27 PM
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From: Cape coral, FL
Torque and horsepower will always cross at 5250. Hp is a multiplier of torque. Prop for peak hp. Then you can play with props for slip and handling characteristics. If you’re spinning a 26 to 5200 and peak at 5400 landing the 26 shoul get you there.
Based on those numbers you listed you’re at 8% slip. That’s phenomenal.
Based on those numbers you listed you’re at 8% slip. That’s phenomenal.
03-26-2019 | 02:03 PM
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Torque and horsepower will always cross at 5250. Hp is a multiplier of torque. Prop for peak hp. Then you can play with props for slip and handling characteristics. If you’re spinning a 26 to 5200 and peak at 5400 landing the 26 shoul get you there.
Based on those numbers you listed you’re at 8% slip. That’s phenomenal.
Based on those numbers you listed you’re at 8% slip. That’s phenomenal.
03-26-2019 | 08:52 PM
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Im not sure. I always assumed seeing it said on spark arrestor rev limit 5250 so never trimmed any higher. It does have d.u.i. ignition so maybe limiter is higher?
03-27-2019 | 01:48 PM
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Carb. 950 Holley. I have never heard it hit rev limiter but previous owner claimed it needed more pitch because it did bounce off limiter and ran low 80s. Maybe I'm not trimmed enough. Can't test for a few weeks because ice still on our lake. Prop has a few dings and not perfect
03-27-2019 | 02:26 PM
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The prop will mess you up too. Always be careful of previous owner claims. Ideally you bump trim speed will increase. Keep bumping slowly until speed starts to decrease. Then bump back down. Lol. That’s the short version. I would stick with the 4blade. Again you’re showing 8% slip which is phenomenal. Maybe look for a new 28 hydro to test also. Thatll drop 400 rpm so you’ll know if it’s a limiter issue. Every inch of pitch I worth about 200rpm.
03-27-2019 | 02:59 PM
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Thanks again for the input. I have had many boats but never above the 70mph mark. I always did it by feel and roost. Kinda hairy looking at GPS and everything will running close to 80 lol. So you don't think the 3blade 27p mirage is worth even trying? I thought if dropped a blade u can run more pitch so that would be a faster prop
03-27-2019 | 04:28 PM
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I personally wouldn’t worry. I mean if you already bought it you can try it. The 3 blade may be able to give you a tick more on top speed but overall characteristics most like the 4 blade. It doesn’t hurt to try. Then you get into a more round ear bow lifting prop like a bravo or a cleaver style stern lifter like a QIV hydro. Fountains do a great job carrying the bow in hull design and seem to really like the hydros. Plenty have had good luck with bravos also. To find the “perfect” prop requires a ton of testing and the perfect top speed prop won’t be the same as the perfect all around prop.
