Estimating fuel usage

[tie_one_on]

Does anyone know where to find fuel estimated fuel usage for a boat. I'm looking at a 1988 28' Baha Weekend Crusier with twin 302 Ford 220 hp Crusader inboards with Velvet Drive transmissions. Trips are usually 30 miles round trip at cruising speed with about 6 hours of trolling. Thanks.

 

[Juhl]

Re: Estimating fuel usage

Expect app. 0,2L fuel per HK per Hour<br />ie. 2x 220 x 0,2L = 88L /H. If you have a powerdiagram you can se how many HK you take out at a specified no of RPM and the then you have your estimated fuel usage.

 

[QC]

Re: Estimating fuel usage

Answers to this question are subjective at best unless you have the data to do Juhl's calcs. Most gasoline V8 small blocks burn around a gallon per hour (GPH) at idle, so your trolling use will depend on your speed and whether you run both or a single unit. Could be as much as 1.5 GPH each if you bump the revs up much.<br /><br />For the Cruise speed they typically burn around 10 - 15 GPH each between 3000 and 4000 RPM on a typical prop load curve.<br /><br />Juhl, What is HK? I know bhp, kW, PS etc. but not HK . . .

 

[achris]

Re: Estimating fuel usage

QC,<br /><br />HK is the Danish way of abbreviating Horsepower. I think also Norwegian and Swedish too. <br /><br />Chris...........

 

[tie_one_on]

Re: Estimating fuel usage

Thanks Juhl & Quietcat. This give me a starting point.

 

[trog100]

Re: Estimating fuel usage

i have seen a formula that went.. 10% of horse power equals gallons per hour.. 10% of 200 hp would be twenty so it would burn twenty gallons per hour at WOT.. and so on..<br /><br />sounds a little high thow praps not..??<br /><br />trog100

 

[QC]

Re: Estimating fuel usage

I just did some quick calcs with some Trailer Boats Mag test data. They range from 6.5% to 8.5% depending on engine etc. All was WOT GPH/rated bhp. There was one two-stroke Rotax that went over 9%.