New Hybrid: Small diesel/ Big OB in 33' S/D Hull.

I love the design, the fuel consumption figures are simply amazing.
just wondering if it's a seaworthy design....the hull form seems to have very little deadrise.http://www.multihulldesigns.com/images/38pwrtriDTLg.gif
Length overall: 38'-0" (11.6 m)
Length at waterline: 37'-6" (11.5 m)
Beam: 16'-11" (5.16 m)
Draft: 1'-6" (0.46m)
Weight: 4,125 lb
Displacement: 5,278 lb (2.394 kg)

Half load, one engine at low mid speed (3,000rpm).
Fuel consumption is 0.407 gph. per engine
Speed is 8 knots.
100 gallons fuel gives 1,965 nautical miles

Half load, both engines at mid speed (4,000rpm).
Fuel consumption is 0.62 gph. per engine
Speed is 11 knots.
100 gallons fuel gives 887 nautical miles

 

I think you have been over complicating things. I have a friend who had a dual drive set up in a trawler running off a layshaft. It had a ford lees of 100hp as an aux, and a cat 3406 as a primary and the layshaft also ran an alternator. Either engine could run the alternator or the propshaft depending upon which pto clutch was in.
Thats all gone now as although the set up worked and had its uses, it wasn't practical and the cost in both machinery and weight and complexity meant its days were numbered. That trawler now is just a standard drivetrain with a kva running everything else.

if you were to pick a slow planing hull shape and power it with the most horsepower for the allowable weight in propulsion gear, and just drive it at your desired speed, you would still havea lot of run for cover capability when needed, and reasonable economy. The maintenance will be less, your boating time will be more enjoyable due to less maintenance.

 

On reflection, I think you are probably right!
No planing boat owner is going to be happy with 7kts cruise, neither are S/D boats used to cruising at 15kts. So it's the old adage....weight is only useful on a steam roller (Uffa Fox).

If you want to cruise at a decent speed with good mpg....small and light it is.
Full stop!