In either lifetime my guess would be about the same amount of fuel was consumed by the speed boat app and the noisemaker app.
FF makes a very good point regarding generators.
Again, owner expectations and lack of understanding of ratings has a lot to do with many of the myths that thrive on internet boating sites.
Take a look at Deere's definition of ratings. Take note of the difference between recreational marine propulsion and marine generator prime mover. The bold typface and color for emphasis is mine.
"
M5: The M5 rating is for marine recreational propulsion
applications that operate 300 hours or less per year and
have load factors* below 35 percent. This rating is for
applications that use full power for no more than 30
minutes out of each eight hours and cruising† speed the
remainder of the eight hours, and do not operate for the
remaining 16 hours of the day.
Possible applications: Recreational boats in the U.S.,
tactical military vessels, and rescue boats outside the U.S.
Marine generator: The marine generator engine rating
is the power available under normal varying electrical
load factors* for an unlimited number of hours per year
in commercial applications.
This rating incorporates a 10
percent overload capability, and conforms to ISO 8528
prime power. Average load over a 24-hour period shall not
exceed 67 percent of the prime rating, of which no more
than two hours are between 100 percent and 110 percent
of the prime rating.
The marine generator rating is restricted to generator
applications only. The criteria used to establish marine
generator application ratings are the same used to establish
industrial prime power generator application ratings."
Those who believe generator engines are somehow rated and operated at lower load factors are very much living in diesel fantasyland. Take the JD 4045 (it is a very common generator drive engine on medium sized yachts) for example ... it is rated to deliver up to 166hp@1800 rpm in marine generator use. That engine displaces 275 cubic inches which, if we subscribed to the half hp to cubic inch myth would be limited to less than 140hp and you can forget about any overload.
The 4045AFM85_D_M4_AP version of the 4045 is rated for 225hp@2600rpm ... do your own calculations on that one.
When we work with a new generator installation we run them on a load bank for 100 hours at varying loads including 10 percent overload while monitoring all parameters. My own system monitors and records power and exhaust parameters and I can attest that those generators live a much harder life than all but a very few propulsion engines that use the same moving parts.