This is an "after the fact" observation, but one key consideration in the extended warranty or not question is how good is your dealer's relationship with the warranty company.
Our dealer has tracked cost vs. benefit on the warranty plans they sold. In every case, the owners who bought the extended plans from Brunswick on complex boats (twin engine, boats with gen & air, boats with powered moving parts like sofas, decks, sunpads, doors etc.) the benefots far exceeded the cost.
But, this dealer is professionally managed, they can fix a boat on the first try, yes, they are expensive, but they stand behind their work and they never fraudulently inflate an invoice.
The warranty co. claims folks aren't stupid and they track the labor hour/parts needed to say, change a seawater pump on an 5.7 L v-8, or replace a coupler. When they get a claim from a dealer that is substantially higher that the norm or contains parts not normally needed for a particular claim, they will require additional info from the dealer to support the claim. Often, the dealer just tells the customer that the claim was not approved rather than being faced with explaining an overstated charge to the warrranty company that was initially refused.
My suggestion is to ask other owners who have purchased the extended plan from your dealer about their success with claims. If your dealer cannot dance with the warranty company, then you are probably not going to be happy with the coverage.