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Name:
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CAT BOAT
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From Boat Maint. forum...
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Date:
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3/21/2008 11:11:24 PM
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This came from BM forum, I thought it might be of some interest to some. Sorry it is so long.
This method/calculation will pretty much give you a good indication within 3 mph or so. You need the following information... Drive unit gear ratio. Propeller pitch. RPM's at wot.
Example Prop.pitch x RPM divided by gear ratio x 1056 minus slip.
Use the info like this... 26" of pitch x 5,000 rpm = 130,000
drive ratio of 1.5 x 1056 = 1584 So, 130,000 divided by 1056 = 82.07. Now, most effecient V-bottoms have a slip around 12-13 percent, and Cat hulls in the 9-10 percent range. (Notice, I said most. And a pontoon boat don't even count because none of them are effecient). Just for kicks, lets say the above boat is V-bottom -- 82.07 mph minus 13 percent slip would come out to about 71-72mph. Sorry this post got so long, but most will find it interesting. All this being said, when your buddy tells you his boat runs some unbelievable speed, walk around to the business end of the boat and gather some information....
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