power to weight

[glen76]

in boat terms with engines, is it an accurate comparison or actual power/speed achieved to compare engine hp as a ratio of weight..

for eg

a 200xs with 20" cs weighs 197kg tf 197/200=0.985 kg/hp
a 200 opti weighs 225kg tf 225/200=1.125 kg/hp
a 275 hp verado 20" cs weighs 288kg tf 288/275=1.042kg/hp

so does that mean the 200xs would still be faster on the back than a 275 verado as it weighs less per hp??? but the 200 opit would be slowest?

if a 200xs was beefed up to a 275hp but maintained same weight ratios it would in theory weigh 270.88kg ie be lighter than a verado??

could this be applied to some of the light weight diesels and in theory mean less is more?? all manufacturers rate a hull to a given hp for o/b with no reference to power to weight..

am i barking up the wrong tree??

 

[Captain Chaos]

and what boat these things gotta push,

surely torque (and therfore prop choice) is a relevant science here?

 

[kitten]

Max rated HP on a hull to pass the RCD and get a CE mark is supposed to be the biggest engine that you can turn the boat at 90degrees in six boat lengths at WOT.

 

[Cookee]

It's ok if you put a sticker on the dash though!

 

[Jon Fuller]

What, a Boatmad sticker?

 

[Cookee]

One that says don't turn 90 degrees flat out! - See you in Poole?

 

[glen76]

say a boat similar to most sportsboat sizes between 6.5-8.5m. I know torque should be taken into consideration but for arguments sake lets not as torque usually equates to aceleration and not top speed doesnt it?? ... as for max engine size for rcd ratings surely that kinda reinforces my point as one 200hp engine could push a boat maybe 5-10mph faster than another 200hp motor.. yes?? no??

 

[glen76]

no one... and i thought u lot were clever