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Old 05-14-2013 | 09:26 PM
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Default formula 311 sr1 rpm

hey guys..i purchased a 1988 311 recently..the props i believe are prob stock..23p bravo..i have the 365 hp which are around 400hp a piece with the little work that have done to them..on gps i hit 68mph at 5200 rpm...is that to high of an rpm for these motors? should i go higher in pitch? the boat planes out awesome and cruises really well also...any input would be great..thanks!!
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Old 05-14-2013 | 10:28 PM
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I have an 89 311 with stock 365 mags with 23 mirage non plus props, I've seen 66.3 on GPS at 5100 rpms with a half tank of gas.
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Old 05-14-2013 | 11:31 PM
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I was checking out props. Not quite sure a few mph is worth 1200 bucks. Lol
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Old 05-15-2013 | 06:40 AM
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Wait till it gets hot out those rpms will come down
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Old 05-15-2013 | 10:57 AM
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My boat with stock 420's and TRS drives ran 68 at 5000-5100 RPM. I wouldn't worry about spinning 365's to 5200. They have the same bottom end as the 420's, and are probably safe to 5400 or so.
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Old 05-15-2013 | 11:25 AM
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I had a 1990 292 sR1 with 365's and I had both 23" pitch and 25" pitch props. I went up to 25" pitch and had the same speed at a little lower RPM, $1,000.00 down the drain. If you don't have aftermarket exhaust, I would save the $1,200.00 and put towards stainless marine exhaust or some other aftermarket system. Also, the 25's will probably hurt your hole shot a little.
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Old 05-20-2013 | 07:31 PM
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I had hydro motive 24s on mine with similar power. You will cruise faster but like stated above when in gets hot revs come down.
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Old 05-21-2013 | 08:35 AM
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Something doesn't seem right. Bravo 23 (really 22) props @ 5200 rpms with a top speed of 68 equals 6% slip, which is not possible. A slip number of 11-13% would be more realistic which would give you a top speed of 64 mph. What have you done to you engines over stock?
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Old 05-21-2013 | 08:51 AM
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Well, they don't make odd numbered Bravo props so he likely has 24's and that gets the numbers a little closer. If you are turning 5200 light then you are almost perfect, put people, a cooler, and fuel in and that will drop down to 4900-5000,
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Old 05-21-2013 | 08:45 PM
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guy i bought it from said diff pistons and cam in motors..said each motor was 400 hp..i lied about props they're quicksilver not bravo and def 23p..i had a half tank of gas 5 adults 3 kidsand against the currant on river rpm gauge on boat said 5200 and gps said 67.9...gonna stay withwhats on it..seems pretty dialed in on taking off cruising and topend
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