FF wrote:If you don't mind paying for the lack of efficiency , which can be 200% to 300% higher fuel burn per hp,
I would love to see the spec sheets on that engine.
Your "efficiency" claims seem to be based on the very small increase in BSFC at lower power but you carefully neglect to provide the information that despite the the minute loss of fuel efficiency, the fuel burn is greatly reduced.
Recreational vessels are not operated for the purpose of reducing the nation's fuel consumption. The way most of us manipulate the throttle probably burns more fuel during a voyage than the microscopic loss of fuel efficiency created by operating at lower power.
Selecting the most extreme position makes for scary reading I guess but you'll have to back up your opinion with some documentation to show things like increased maintenance costs and 2 or 3 times the fuel burn per HP at reduced power. According to that fantasy, a marine diesel engine driving a fixed pitch propeller might burn the same quantity of fuel just above idle as it does at full power.
EDIT:
Just for grins I ran the numbers on one of those monster 400 hp engines, and a Detroit just to make it a real worst case.
According to the Detroit Diesel specifications for a 6V92TA driving a well matched fixed pitch propeller, the brake specific fuel consumption (BSFC) at 425 hp is .387 pounds per horsepower hour, a pretty good figure that equates to about 23.5 US gallons per hour.
If we slow that engine down to the lowest continuous output that DD plots, and by inference, an approved operating condition, the BSFC increases to .49 lb per horsepower hour which equates to 3.5 US gallons per hour.
The increase in
fuel consumption per horsepower due to lower fuel efficiency at the lower output is
.014 gallons per horsepower over what it would burn if it had the same BSFC as it did at full power.
That is also equal to about .7 gallons per hour for the entire 50 hp over what the engine would burn if it had the same fuel efficiency at 50hp as it does at 425.
*
-- Edited by RickB on Sunday 10th of October 2010 09:14:29 AM