Estimate of top speed
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URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=21060
Printed Date: January-11-2025 at 10:39am
Topic: Estimate of top speed
Posted By: OverMyHead
Subject: Estimate of top speed
Date Posted: March-27-2011 at 1:29pm
I found this formula in a boating magazine
Horsepower/ gross weight = X
Sguare root of X = Y
Y x 250 = Theoretical speed
Theoreticaal speed x .9 = Actual top speed
so my boat has 240 horse power and loaded up with two and gear grosses around 3000 lbs plugged into the formula it should have a top speed of 63.63 mph. So what is different about our boats?
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For thousands of years men have felt the irresistible urge to go to sea, and many of them died. Things got better after they invented boats.
1987 Ski Nautique
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Replies:
Posted By: hotboat
Date Posted: March-27-2011 at 1:37pm
The angle of the prop and amount of drag from our snowplow type of boats is much more than a vhull io or outboard and they can trim the drives for starters
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Brian
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Posted By: harddock
Date Posted: March-27-2011 at 5:27pm
I have a radio controlled twin weed wacker powered boat. 60" long may be 20 lbs. with quiet exhaust it will top out @ 31mph. with tuned pipes (no additional weight) it will up that to right around 44mph. How does that figure into your equation?
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http://www.correctcraftfan.com/diaries/details.asp?ID=4487" rel="nofollow - 1998 Ski Nautique
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Posted By: OverMyHead
Date Posted: March-27-2011 at 8:56pm
Better check your props, my calcs assuming a total of about 2.5 horse power should have you at 80 mph. The tuned pipes seem to have an obvious effect on your horse power.
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For thousands of years men have felt the irresistible urge to go to sea, and many of them died. Things got better after they invented boats.
1987 Ski Nautique
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Posted By: harddock
Date Posted: March-28-2011 at 10:12am
My weight estimate could be way off. Boat weight could be 50lbs. The point was that there are many more variables that will change max speed. Hull style alone will effect top end.
If you but a 2500lbs 20 dd inboard with 310 hp against a 2500lbs 20 catamaran with 2 150 mercs you'll see a certain differance in top end.
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http://www.correctcraftfan.com/diaries/details.asp?ID=4487" rel="nofollow - 1998 Ski Nautique
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