Let's see here. Prototype #1, XF6F-1 (02981), was first flown on June 26, 1942. It had a Wright R 2600-16 engine and a Curtiss electric 3-bladed prop which produced 1,600 HP at 2,400 rpm.

The second prototype Hellcat (02982) had a Pratt & Whitney R2800-10 engine and a Hamilton Standard 3-bladed prop.

The first production Hellcat, spinning a Hamilton Standard 3-bladed prop, took to the air just five months after the flight of the second prototype. There were no mention of either prototype spinning a 4-blade prop.