Power to weight ratios for performance and economy

[PCUK]

My previous SD boat displaced 14 tons and with 300hp could manage 12 knots max' and ten knots cruising at 1 gallon per mile. My latest acquisition is a medium vee planing hull and displaces about 2.5 tons and is about to be re-powered with 250hp. I'm hoping for sparkling performance and hugely better economy but what are the likely figures going to be from the experience of owners with similar boats?

 

[Spi D]

What make & model is your new boat?

 

[PCUK]

Reinell V-204 1978

 

[Scarron]

There is no doubt it's going to be a lot better, what engine and drive are you going to fit?

 

[dpb]

About 30 knots with 2 to 2.5 mpg over all if petrol - that was a 1986 Sea Ray 250 with 5.7 V8 carb petrol

 

[Spi D]

Searched my archive without much luck. Hull definately is modified V and looks good, with proper strakes. The modest depth of the V makes it pretty fast for it's type.

2.5 T displacement must be your guess? If you can supply the ready-to-go weight (ALL inclusive) it will be possible to estimate the top speed. If you also state the sterndrive gear ratio, a suitable prop pitch can be calculated as well.

 

[PCUK]

I'll be putting the finished boat on a weigh-bridge before choosing the props. ratio is 2.2:1
Engine Vetus Vf5-250 - Drive Bravo 3x.

 

[Spi D]

Sounds like a nice powerpack

If you get the boat weight and add water, fuel, crew and gear the total weight and given specs will make it possible to calculate prop & speed.

 

[PCUK]

Thanks for that. It'll be a while yet.