Twin 300 verado

[Actionboat.dk]

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.

[Andy Moore]

Sexy looking outboards. Nice.

[Nauti Buoy]

Originally Posted by Actionboat.dk

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.

[joakimhansson]

Actionboat.dk

Do you think you can get more in performance? The 300 have another ratio than the 275 so maybe it´s 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...

Can´t look much better than your "actionrib"..... Good luck.

[Fjordrafting]

Originally Posted by Actionboat.dk

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.

[qcamel]

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

[Hugh Jardon]

http://www.mercurymarine.com/engines...ecs.php?ID=127

[Actionboat.dk]

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

[codprawn]

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!!!

[ribit]

Originally Posted by codprawn

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