My 23

[Fr. Frank]

NOW you can say you have seen them turned in TWICE.

Okay. I have seen them turned in twice.

Seriously, I was part of the team that did the factory prop setups for Mercruiser sterndrive and Mercury and Yamaha outboard powered Wellcraft Scarab and Excaliber offshore boats in the mid-late 80's. While we discussed inward rotation, we decided against it because of the "P" factor. As I recall, some slide-rule engineer calculated a 3-4% loss of thrust from submerged inward rotation, a loss not present with surface-piercing propellers and running semi-submerged.

Which, by the way, is why the standard twin engine setup for the 27' Wellcraft Nova II and 26' Wellcraft Antigua back '86 to '89 was Mercruiser 350/260's with two RH Alpha drives. Counter-rotation was offered as an option. Best performance and the standard factory setup was with twin RH 23"P surface-piercing thru-hub Cleavers, so rotational direction/ "P" factor wasn't really a issue. With CR drives, we used outward rotating ventilated Mirage propellers.

I will say this, I have seen CR props installed by a dockhand onto the wrong lower units on twin Zuke 250's after 100hr service. That was just two weeks ago. The owner shoved the controls forward and promptly backed into into the dock, cracking both cowlings.
Needless the say, the Marina owner wasn't happy about having to give the guy new cowlings. On the other hand, you should never put your boat in gear and throttle up at the same time right at the dock, without clearing the dock and other boats first.