On Fri, 28 Mar 2008 23:06:32 GMT, Short Wave Sportfishing
wrote:

Therefore an appeal to the group for the following questions.

What is the net effect of increasing diameter with the same pitch?

More thrust, greater prop efficiency (less slip), requires more torque
(horsepower) to maintain the same RPMs, more vibration if tip
clearance is insufficient.

What is the net effect of increasing/decreasing the pitch with the
same diameter?

Greater forward motion with each turn, more slip unless a light easily
driven hull, requires more torque (horsepower) to maintain the same
RPMs.

Either should cause speed to increase by some amount if RPMs can be
maintained.