HK wrote:
Richard Casady wrote:
On Wed, 02 Jul 2008 23:46:08 +0000, Larry wrote:

In a Sea Rayder 16' jetboat, the 175hp, 6-cylinder Sport Jet will
guzzle around 14-20 gallons a day, especially if you drive it like
you stole it or pull skiiers for hours.

That statement is useless without a time factor better than 'per day',
Eight hour day would be maybe 2 gallons per hour. I don't think that
is what you meant.

Casady


Really, and 14-20 gallons wouldn't be that much for any boater with an
engine around that size who ran at a high cruise or was pulling tubes or
skiers.

You don't pull skiers, wakeboarders or tubes at high cruise.

I've read that the jet boat's impeller system is about 30% less efficient
than a similarly powered outboard. Does that mean that a jet boat will get
beat by an outboard, or just use more gas?

I've got a Whaler Rage 14, and skipping along at 25-30mph it seems efficient
when lightly loaded.
It will go through 5 gallons of gas after several hours of mixed running,
but I haven't done any extended runs that would allow me to measure the mpg.

On Fri, 4 Jul 2008 08:15:19 -0400, "Floyd"
wrote:

I've read that the jet boat's impeller system is about 30% less efficient
than a similarly powered outboard. Does that mean that a jet boat will get
beat by an outboard, or just use more gas?

The jet will have a lower top speed. It will burn more fuel at any and
all lower speeds.

Casady

"Richard Casady" wrote in message
...
On Fri, 4 Jul 2008 08:15:19 -0400, "Floyd"
wrote:

I've read that the jet boat's impeller system is about 30% less efficient
than a similarly powered outboard. Does that mean that a jet boat will
get
beat by an outboard, or just use more gas?

The jet will have a lower top speed. It will burn more fuel at any and
all lower speeds.

Casady

It will burn more fuel. May or may not be faster. There are different type
pumps. There are axial flow, low pressure pumps that are slower speed, but
handle white water better at reloading up after losing intake water, and
there are the high pressure pumps that are faster. Kodiak and Hamilton are
examples of the first, Berkeley and American Turbine are examples of the
second. Jet ski pumps are probably the most inefficient of all the pump
designs. Small engine and high RPM's trying to move lots of water through a
small impeller pump. The newer Hamilton 212's etc are about 95% efficiency
of props.

On Fri, 4 Jul 2008 15:19:27 -0700, "Calif Bill"
wrote:


"Richard Casady" wrote in message
.. .
On Fri, 4 Jul 2008 08:15:19 -0400, "Floyd"
wrote:

I've read that the jet boat's impeller system is about 30% less efficient
than a similarly powered outboard. Does that mean that a jet boat will
get
beat by an outboard, or just use more gas?

The jet will have a lower top speed. It will burn more fuel at any and
all lower speeds.

Casady

It will burn more fuel. May or may not be faster. There are different type
pumps. There are axial flow, low pressure pumps that are slower speed, but
handle white water better at reloading up after losing intake water, and
there are the high pressure pumps that are faster. Kodiak and Hamilton are
examples of the first, Berkeley and American Turbine are examples of the
second. Jet ski pumps are probably the most inefficient of all the pump
designs. Small engine and high RPM's trying to move lots of water through a
small impeller pump. The newer Hamilton 212's etc are about 95% efficiency
of props.

Our Turbocraft is axial flow, and in fifty years has never sucked air
into the intake. Weeds once. Once the ski tow rope. Had to turn the
engine and pump backwards, with a pipe wrench on the driveshaft, to
get it out. The pump is a licenced copy of a [New Zealand] Hamilton.

Casady