PSSA follows the corinthian spirit. Most of our races include skippers taking their own finish times (due to our finish locations), so to seal shafts runs counter to our culture. Skippers will just be cheating themselves by using the engine. We also have rules against sponsorship.
That said, cheating has happened, even in a race around the world. Richard Konkolski in the 82-83 BOC was suspected of motoring in the doldrums, then again in the '86 BOC. He was protested on the basis of his outsized daily runs in the doldrums and a protest meeting was held in Cape Town - hang in here, there is a point to all this. From Hal Roth's notes of the Protest Hearing:
"Jean Luc and I were both convinced that Konkolski used his engine in the doldrums, and we counted on the race committee's engine seals to convict him. We were both furious when we found that the committee had simply put a wire with a seal on the engine gearshift lever. To defeat the seal, you merely had to disconnect the gearshift lever from the engine, and shift gears with a pair of pliers."
The protest was thrown out. Most felt Konkolski should have been thrown out, but they decided there was not enough proof.
I have no answers. Shafts or levers were not sealed in 2012, and skippers using them for propulsion never crossed my mind. I am surprised that a crewed race would require shaft seals, but maybe it's sponsorship money that applies such pressure to win & keep crew members quiet? The duty of the RC is to run a fair race, so unless it's onerous, they should err on the side of fairness. It turns my stomach, though. Ironic that the race starts at the Corinthian YC. I would kill the seals if skippers were expected to take their own finish times.