On Sun, 29 Apr 2007 19:27:48 -0400, "Eisboch" wrote:

The difference is the speed at which you play. Consider the differences in
a couple of boat examples:

Boat "A": 25' something with a 225 hp gas outboard or a 300 hp I/O setup.
Boat displaces about 5K-6K lbs. With a couple of people aboard plus "stuff"
what is it's fuel burn at "cruise" which is probably 32-35 kts?

Boat "B": 50' something with twin, 370hp turbodiesels. Boat displaces
38k-40k lbs. With any legal number of people aboard plus all their "stuff"
what is it's fuel burn rate at "cruise" which is 18-19 kts?

Betcha Boat "B" (which is over 7 times heavier) is burning fuel at a
comparable rate to boat "A".

If so, which boat is more efficient?

It's easy enough to balpark the numbers.

I happen to own a Boat "A", SeaRay 270 Sundeck, actually 26.5 ft, 5800
lbs dry, 320 hp I/O gas. It cruises 25 to 30 kts and burns 12 to 15
gph, averaging a little better than 2 nautical miles per gallon.

Boat "B" will typically burn 25 to 30 gph averaging about .7 nautical
miles per gallon.

So in theory Boat "A" is about 3 times as efficient ignoring weight.

Boat "B" however is 6 or 7 times heavier so on a per pound basis is
about twice as efficient as Boat "A".

It all depends what your boating objectives are.

My experience with larger boats indicates that fuel costs are a
significantly smaller percentage of annual operating costs. As an
example, on our GB49, fuel costs are less than 30% of annual, even in
a year where we burn 5,000 gallons. The big numbers other than fuel
are maintenance, depreciation/amortization, and insurance. If I had
to pay for marina storage that would reduce fuel percentage even more.

On the 26 ft I/O however, fuel costs are over 50 to 70% of annual
doing ball park calculations.

Based on all that, I'd conclude that higher fuel prices impact small
to mid size boats more than larger ones.