On Sun, 16 Dec 2012 10:32:22 -0600, "James"
wrote:

Hi Group, I have an actual boating question as opposed to all the
political crap on the list now. On the average what kind of gal/hr
usage would I be looking at with either a single V-8 or twin V-8s and
probably Volvo drives, probably small block Chevy at say between 10 to
15 knots cruise in a 27' to 30' flybridge cabin cruiser? Thanks, Jim


You are asking what is essentially an unanswerable question.

The fuel consumption of a small block chevy will depend on:

Carbureted or injected engine
Even the model of carburetor will effect fuel consumption.

Displacement:
Small blocks were built in sizes ranging from 265 cu. inches right up
to 400 cu. inches.

Rpm that the engine is operated at.

And,

LWL of boat

Weight of boat

Type of hull - planing, semi-planing, deep hull displacement, shallow
hull displacement, etc.

Weather: wave pattern, prevailing wind during voyage, etc.

Current/tide: Going up the river - or down the river.

Condition of bottom - smooth and hard bottom paint? Marine growth? and
so on.

Basically a internal combustion engine's fuel consumption is a factor
of the horse power produced and the RPM at which it is being produced
but unfortunately the usual installation lacks the instrumentation
necessary to measure these values.

The usual method is to fill the tanks and then make a fairly long trip
and than top off the tanks to determine how much fuel was used to
arrive at a gallon/hour figure. Which would be an approximation and
will vary considerably depending on conditions.
--
Cheers,
Bruce