Tonguez
A suffusion of yellow
If you remove the stowaway and then play a cruel captain and dissatisfied crew then you still get a plausible but not an assured mutiny. Theres nothing to foil except the dissatisfaction of the crew
actually I was thinking on this, if you made the captain enough of an abusive tyrant could you may encourage the PCs to lead the mutiny themselves? Give them a reason to oppose the captain (maybe he decides to execute a crewmember for something petty), the PCs step in, the captain draws his sword - battle happens and ship wrecks