"Extended “warranties” you have to buy aren’t really warranties; they’re service contracts.
A true warranty offers broad coverage and has the weight of state and federal warranty laws behind it. Service contracts, on the other hand, are really insurance policies generally underwritten by third parties, not manufacturers, and are regulated as such in most states.
Service contracts have limitations that true warranties don’t. A service contract may cover a broken alternator ($650). But it probably won’t cover consequential damage (when one part causes another to be damaged), so it won’t pay if the alternator damages the engine control unit ($1,300), leaving an owner to pay the difference.
Having a service contract won’t protect you from out-of-pocket expenses. Service contracts, like health-insurance policies, usually come with deductibles, often between $25 and $50 per incident. Many contracts don’t pay to remove the engine from the boat or have the boat hauled if it’s required for repairs, so there may be additional expenses for that.
Most service contracts aren’t backed up by manufacturers. Third-party insurance companies usually
write the contracts, and manufacturers and dealers typically won’t step in to help if there’s a problem. On
the other hand, factory-backed programs have agreements with their dealers; the factory is ultimately
responsible, so you should expect better service when there’s a problem.