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Old 22 September 2007, 12:24   #1
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Twin 300 verado

had the new Verado's 300 fitted on the rib. (about 20 hours)
Achieve 68.2kn with 25* revelution props about 1,3kn more than the twin 275
has a little more power midrange. On the acceleration it is the same.
both rig up for charter.
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Old 22 September 2007, 13:23   #2
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Sexy looking outboards. Nice.
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Old 22 September 2007, 17:29   #3
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Quote:
Originally Posted by Actionboat.dk View Post
had the new Verado's 300 fitted on the rib. (about 20 hours)
Achieve 68.2kn with 25* revelution props about 1,3kn more than the twin 275
has a little more power midrange. On the acceleration it is the same.
both rig up for charter.
Very nice, can't wait for mine now.
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Old 22 September 2007, 19:01   #4
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Actionboat.dk

Do you think you can get more in performance? The 300 have another ratio than the 275 so maybe itīs little harder to find the right prop?

How many hours did you use your last 275hp verados... Why change?

It does not sound so much with +1,3 knots and the same performance in the middle...

Canīt look much better than your "actionrib"..... Good luck.
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Old 23 September 2007, 05:27   #5
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Originally Posted by Actionboat.dk View Post
Achieve 68.2kn with 25* revelution props
both rig up for charter.
Hi!
Could you please help me out here, because there is something I do not understand.

That speed is normally not possible with that pitch on the propell. If you should get that speed 68.2 knots), you would need a slip-percentage of 5.8% at 6500rpm!!!
Normal slippercentage is 12-15% for a 29 feet rib with twin engines fitted for chartering 12 people.

25" (pitch)x2.54 (inch) =63.5cm pr rev.
Rev pr hour is 6500 (min) x 60 (minutes) 390.000

63.5x390.000= 24.765.000 (are number of cm pr hour.)

The gearratio is 1.85

24.765.000:1.85= 13.386.486 cm pr hour

13.386.486cm pr hour is 134 km/t

134:1.85 (knots) = 72.4 knots pr hour.

This is if there is no slip.

A slippercentage of 12, which is the best you nomally can get, will give you a speed of 72.4x.88=63.7 knots.



You claim to have a slip of only 4.2 knots that is (4.2:72.4)=5.8% slip!

We both know that normally it is not possible.

How do you get that speed? Are your engines doing more than 6500 rpm, are you going with the current, wich has a speed of 4.5 knots or is there any other solution to this that I do not understand?
Sorry to ask, but interested in learning.
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Old 23 September 2007, 06:25   #6
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Cannot be bothered doing all the maths but the new 300's have a 1:75 ratio not 1:85, they differ from the other 6 cylinder verdo's
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Old 23 September 2007, 08:26   #7
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http://www.mercurymarine.com/engines...ecs.php?ID=127
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Old 23 September 2007, 11:33   #8
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I use TSpeed.exe to do all the mat.

12-15% sound much to me. the figer I get out of TSpeed is 3-4% So can only say what the gps show. remember lot of it is the setup.(engine and boat)
300 have 1/1,75 and 275 have 1/1,85.
We are doing 67kn with the twin 275 with the 25* revolution. 6350rpm.
We just mounted the 300 with the same props. That also why they have the same bottom accelleration.

You are welcome to come and try the speed.

Br Jan
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Old 23 September 2007, 11:42   #9
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Fjordrafting obviously didn't know they had changed the gear ratiio. When you work it out with the correct ratio it is about 9 - 10% slip which sounds about right.

Talking of gear ratios I still can't work out why suzuki have stuck their necks out on their big 4 strokes and gone for a 2.08:1 ratio - everyoine else seems to be going the other way!!!
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Old 23 September 2007, 14:27   #10
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Quote:
Originally Posted by codprawn View Post
Fjordrafting obviously didn't know they had changed the gear ratiio. When you work it out with the correct ratio it is about 9 - 10% slip which sounds about right.

Talking of gear ratios I still can't work out why suzuki have stuck their necks out on their big 4 strokes and gone for a 2.08:1 ratio - everyoine else seems to be going the other way!!!
maybe they have gone for the heavy type of plodding boat as they consider they have a plodding engine rather than the speed freak
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