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Below is what I read initially which says "under normal operating load", which is why I figured I needed at least a half tank of gas/gear and a could more people (normal for me). I will play around with this some more though just to be sure.
From what I have read Zacs, I am making the engine work harder by not being in the optimal rpm range for it. I recently spun the hub of the 15/17 prop, not sure if related or not but it caused me to do this testing to see where I am at.
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The goal in prop selection is to determine what propeller style and size will maximize performance for your boat, while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum RPM where maximum horsepower is produced.
Run the boat/motor at w.o.t. under normal operating load to determine the maximum RPM you are able to obtain. A tachometer is necessary for this test. Adjust the motor trim angle for the optimum performance. If during this test, you begin to exceed the maximum rated RPM of the engine, reduce throttle setting to a position where maximum RPM is not exceeded.
If your test results in your being able to over-rev the engine, you need to increase the pitch of the propeller. Increasing the pitch increment by 1" will result in approximately 200 RPM drop. If your testing shows, however, that you are only able to obtain a RPM somewhat lower than the maximum rating given by your engine manufacturer, you would need to decrease pitch. Decreasing pitch would increase your RPM.
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