The used market last year was red hot and all indicators are that it will continue to a seller’s market in 2021.
Personally, I would not give away money on a dealer trade-in in this market. If you’re willing to put in a tiny bit of effort, you will get TOP dollar in the spring by selling it yourself. Unless the dealer is giving you a REALLY generous trade-in offer (which I doubt), you could be giving away a LOT of money in the current market.
I watch the used market pretty closely and in CrazyTime (April 1 to June 1), boats disappeared last year seconds after they were posted. Any boat in running condition without major issues noted in the ad would sell within hours or days. I personally sold an outboard and my phone was on fire from 3 minutes after I posted it. Nobody even bothered to try to negotiate with me on price. Make the boat spotlessly clean and fix all those “easy fix” items NOW. Clean + everything works = top dollar.
The way I look at it, it’s my money. Shady/not shady, I don’t see it that way, it’s business.
With that said, I agree with Ralph above. If your purchase agreement with the dealer is based on a trade, I would want to tell them you decided to sell it yourself and make sure that doesn’t go against anything you signed.