Speed and prop size?
hi my 1999 z258 limited edition with a 7.4 merc and bravo 3 leg has 22 pitch props bu t will only turn 4000 rpm with a speed of 40 mph does anyone know the factory spec for rpm and prop size what speed are someothers getting with this boat set up thanks
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Re: Speed and prop size?
What's your elevation? I have a 2000 Shabah 250 (similar to the 258) with a 7.4 and a bravo 1. I run a 19p 3 blade at 5000' elevation. I managed to hit 51mph on Saturday at 4600rpm.
Seeing as you are at 4000 rpm you are missing out on 400-600 rpm which would benefit you a few ways. Dropping your pitch would get you on plane easier and get you a little better top end, maybe 45-48 ( just a guess!). You would also use less fuel due to the quicker plane times. Then again, depends on the load in the boat. (Number of people, gear, ice chests, fuel, etc) Sent from my DROID RAZR HD using Tapatalk 2 |
Re: Speed and prop size?
Sorry to not answer the last question. Your 7.4 WOT should be 4200-4600.
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Re: Speed and prop size?
the elevation is 1200 feet as in the weight one or up to four people the prop is 22 mec 48-823663 and 48-823664
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Re: Speed and prop size?
i need to compare the same drive and ratio as my boat is a 1999 shabah z 258 cuddy 7.4 bravo three 2.0 ratio with 3 blade stainless 22 pitch 15 inchs running wot 3800-4000 i only get 38-40 mph at 1100 feet alivation and light load 2 people in boat rpm checked motor fine low hrs and speed was gps thinking of changing the drive to 2.2 ratio if it would help
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Re: Speed and prop size?
The 2.0 gear ratio is the one normally used in these situations. It might be less expensive to buy a set of 20" props and use those. That will bring your rpms well into the recommended range.
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