What's your prop's pitch? You see cavitation under those conditions if you back off on the throttle?

   If I back off on the throttle it stops cavitation.  I don't know the prop pitch, but I think it is he standard pitch when you buy one of these motors.  I'll look at it tomorrow. To getmore quantitative data.

You'll have to do some interpolation with this:

https://marine.honda.com/parts/propeller-calculator

- as I doubt the PM's hull design is a specific choice here!

Still, as with a wheeled vehicle, the prop's pitch (sprockets on a bicycle; gears, final drive & wheel size on cars & trucks) is a vital factor in determining efficient transmission of energy from the motor to effect hull propulsion over as wide a speed range as is practical.

Erm, sorry - meant to type Peeler above where I keyed in PM.

And here's an active link to that Honda calculator.

(Sure wish this forum's software permitted editing one's posts... sigh.)

Do you have a 20" shaft motor per the design?   see, http://www.clcboats.com/shop/boats/powerboats/peeler-outboard-power-skiff.html

from the CLC, Peeler Skiff FAQ

"Is it a long- or short-shaft outboard?

The Peeler Skiff is designed for a long-shaft outboard (20 inches).  It would be difficult to modify the boat for a short-shaft, and doing so would adversely affect the boat's reserve flotation. "

   Propellor cavitation or ventilation?  Ventilation is where you suck air down and through the prop.  Cavitation is where the water forms vapor bubbles in the low pressure regions of the prop that then collapse, "pinging" or rattling the prop.

Ventilation is likely if you have a short shaft engine so don't have the prop low enough in the water.  Cavitation is more likely if you have too high a pitch (the "standard" prop as opposed to the "power" prop which is for slower boats w/ higher thrust).  My bet is ventilation.

I've had ventilation in the Peeler Skiff in chop; the prop surges and makes a dreadful sound. Air was getting under the bottom and reaching the prop.

This always happened when I had weight too far aft in the boat, and went away when I shifted weight forward. 

After we installed the center console in ours, the problem went away entirely. I guess because this gets the crew weight quite a bit further forward than you can even with a tiller extension.

But also around that time we bolted "Doel-fins" to the lower unit of our outboard. This helped a great deal in leveling out the lightweight Peeler Skiff at higher speeds, and may have done as much as adding the center console:

These are inexpensive and quick to install.

Doel-Fins:  http://www.davisnet.com/product/doel-fin-stabilizer-fin-black/

   To answer all that kindly replied to mu query-  the pitch on the prop is 10; the motor has a long shaft (20 inches); the problem clearly is ventilation, not cavitation as I previously stated.

   Added a set of Doel-Finns.  Problem seems to be solved.  Thanks for the suggestion.