Thread: Diesel Economy
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Old 08-30-2015, 10:57 AM   #12
DavidM's Avatar
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 5,022 gives fairly rigorous fuel consumption figures for various boat and engines. Modern common rail diesel engines typically are reported as producing 20 hp per gph of fuel at wotwhich is consistent with manufacturer curves. And if you look at curves for older non common rail engines, these range from 17 to almost 20 hp per gph at wot.

Four stroke, fuel injected gasser inboards are reported by Boattest to produce about 12 hp per gph at wot. The gasser may be penalized a little bit by measuring at wot but that is the only way to know exactly how much horsepower is being produced because gasser manufacturers never publish hp and fuel consumption curves.

But with precise fuel air ratio provided by EFI, I don't think it makes that much difference at wot vs lower power loadings compared to the days of 4 bbl carburetors that dumped fuel like an open hose into the engine at wot.

FWIW four stroke outboards produce 10-12 hp per gph according to Boattest and of course some of them are auto engine derivatives so that isn't surprising. Even the 2 stroke Evinrude E-Tec engines get 10 hp per gph.

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