On Jun 21, 7:24 am, R Swarts wrote:
Over the years I've seen very little written about fuel economy in
boats. If anyone has good data I would like to see it. I am particularly
concerned with optimal speeds for planing hulls. Is it in the
displacement range? Or on the plane? Does it increase monotonically with
decreasing speed? Not in gallons per hour, but in miles per gallon. If
one has a twin screw boat, does fuel economy increase or decrease in
running only one prop? Is diesel always more economical than gas? And
anything else that bears on the problem.

Bob Swarts

When I sold boats for Bayliner at Olympic Boat Center I was taught
that their hull was supposed to adjust itself to the most efficient
plane for the amount of throttle given to the prop. Sounded to me like
a bunch of sales talk.
I have crossed the Gulf of Alaska around 80 times in many types of
vessels and have found 8 knots to be the most economical speed to run.
I can monitor the day tank and measure gallons per day and nautical
miles covered.
Diesel is always more economical than gasoline all things being the
same. Load, distance, same boat etc.
Also, all the new fuel technology is for diesel engines, because
diesel engines can run on many different things. Rudolf Diesel even
tried to run coal dust, but he had too much trouble metering it and
injecting it. The diesel engine can even run on peanut oil. I haven't
tried it yet, but as soon as I buy an old diesel car I am going to try
it. You can buy vegatable oil from discount grocery stores cheaper
than Diesel fuel. I would like to see if it can be mixed! I have heard
that just adjusting the pump is the only modification required.