This is one of those situations that most certainly has created a lively and
interesting discussion. It reminds me of a long time airline captain that
asked, "You have two identical airliners at the same altitude, and same
airspeed, but one plane weighed 50,000 lbs more than the other (easy with
the 747s he used to fly). Now, both airplanes lost all power at the same
time...which would glide farther?"

The answer seems obvious...or is it? Same with the prop discussion here.

--Mike

"Shortwave Sportfishing" wrote in message
...
On Sun, 26 Feb 2006 17:00:28 -0500, "RCE" wrote:


"Shortwave Sportfishing" wrote in message
. ..
But, just as a discussion exercise...

Everybody is forgetting how we got to 6,000 RPM. All else being
equal, more horsepower will get you to 6000 RPM faster with the net
result being more end speed at 6000 RPM. Once the boat is planing and
the boat is approaching 6000 RPM horsepower beings to show up
resulting in a higher end speed.

Yes/No?

IMO, yes .... and no.

The bigger engine will get you to 6000 RPM and the speed that 6000 RPM
produces - faster.
The smaller engine will take longer to get to 6000 RPM, but when it does,
the boat will be going the same speed.

So .... if it were a drag race, the big engine wins.

But for obtaining and maintaining a speed that 6000 RPM produces, both are
the same in this particular example.

You are discounting inertia and momentum as a factor. More horsepower
will overcome base inertia and add momentum meaning that the larger
engine will have to work less to maintain, or even increase, speed
given the same RPM.