The propeller on your vessel has a pitch of 22.8 feet. From 0800, 18 April, to 1020, 19 April, you steamed an observed distance of 403.6 miles. If your average RPM was 74, what was the slip?

Correct Answer: Option B — +8.0%

Total time is 26 hours and 20 minutes (26.333 hours). Engine distance: (74 * 60 * 26.333 * 22.8) / 6076.1 = 438.7 miles. Slip: (438.7 - 403.6) / 438.7 = 0.080, or +8.0%. This represents the efficiency loss between the theoretical propeller advance and the actual distance made good over ground.