Extended Warranties
I have been in the trade for 30 years, and ran a boat yard for over a decade; I've had my share of experiences with extended warranties. While running the yard, from time to time an owner would want to use a 3rd party extended warranty to cover repairs or a failure. Typically, the only plans a non-dealer could act on were the after-market, 3rd party versions, and in virtually every single case, they had so many loop holes and outs for the warrantor that they were all but worthless.
Reading a policy, something I did recently for a client who was considering one, is very enlightening. For instance, coverage is void if you do any work yourself, on any part of the engine, including oil changes, it all has to be done by a dealer and documented. Sort of makes sense, but unless you read the policy you may expose yourself to denial of coverage.
We never accepted them in lieu of payment, we would bill the customer and they would submit the claim to the warrantor, and were nearly always denied or only a small fraction was covered. It's truly a case of buyer beware, if you are offered a marine extended warranty, first determine if it's provided by the OEM or a third party, and if the latter do your due diligence, including reading the policy and independent reviews before proceeding.
Years ago, when I was working as a mechanic, a client's Mercury Bravo stern-drive had a catastrophic failure of the internally lubricated parts, a clearly covered item, on a very pricey part. He submitted the claim to the warrantor and they said, "You don't have a policy with us". The dealer from whom he purchased the policy pocketed the premium and never submitted the paperwork to activate the policy. The dealer had also closed its doors since selling him the boat, however, he was very resourceful (pre-internet) and tracked the principal down, who had opened a new dealership in a different part of the state and basically said, "cover the repair or I'm calling the state insurance bureau". He had a check in short order. Bottom line, if you pay for an extended warranty, confirm it's been activated.
OEM extended warranties from engine manufacturers are another matter entirely, all the examples I've encountered are legitimate and cover legitimate failures without a lot of loop holes. For modern, electronically-controlled diesel and outboards they do, in many cases, make good sense and are cost effective.