Eric, it looks like there are some errors in you guess at derived BSFC for this engine. According to the only spec I could find for this Perkins engine the BSFC at medium power will be around that 210 to 220g/kWh figure I gave earlier (it runs at around 190g/kWh peak), which equates to a thermal efficiency that's a fair bit better than 20% (which doesn't seem too surprising, as even some fairly crude diesels manage better than 30% at medium power levels and this Perkins was derived from a tractor engine, designed to operate at good efficiency for long periods at medium power levels).
My estimate, using BSFC directly, indicates around 15kW, or 20hp, for 1 US gallon per hour. 10hp indicates a BSFC of around 420g/kWh which is much poorer than even a two stroke gasoline engine; in fact it's typically the sort of BSFC that an old generation turboprop engine gives.
Sorry for the non-US units, BTW, my brain is firmly wired into using SI units, so I need to back convert to get to things like gallons and hp!
Jeremy
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Hi Michael,
>
> For gasoline, the conversion is GPH = 0.0226 * HP / TE. Diesel contains 115% the BTUs of gasoline.
>
> If we assume a 20% Thermal Efficiency for your engine at low RPM (just a guess), we get 1 * 0.20(TE) / 0.0226 = 8.8hp * 1.15 for diesel = 10.1hp
>
> That's 7.6kW. If you look back at post #19718, my answer was that you could expect a 16kW drive to push your boat at 7kts. Half the power and slow down 1 knot means 6kts = 8kW. Two completely unrelated calculations that come up with the same answer +/- 5%. Weird, isn't it.
>
> You can keep coming up with different ways to ask the question, but the answer is going to keep coming out the same.
>
> At least this answer is better than the 43hp that you guessed on your next post...
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
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