Curious about pricing for a boat

Okay, so we are trying to sell our 1996 Sea Ray Sundancer 240. I came up with a roughly 21-23k value, but my dad said that he found it to be worth less.

If I had pictures, I'd post them, but I'm kind of a ways away from the boat right now, so that won't be happening.

The boat is in great condition. There's nothing wrong with it that can't be fixed with cleaner. The entire cabin area is immaculate, minus a flaw where the plastic panel on the refrigerator is too big for the fridge itself, so it's all bent up and crooked. which is odd because it came like that... Anyways, here are the options:

Depth Finder
Transom Shower
New AM/FM CD Player with 6-8 speakers
Never used head.
Electric Range
Refrigerator
Sink
I think the engine is a 212 Mercruiser
Single Prop
Transom Swim Platform w/fold down ladder
Dual Battery
Fresh Water Hose system
Hydraulic Trim
Soft Camper Top w/ plastic windows all around
Bimini Top
15 foot cover for main deck
Snap in carpet

I can't think of anymore options right now. I've used NADA, but that doesn't actually have any kind of options for some of the things that this boat has, which is slightly frustrating. So yeah. Any ideas about what it would be valued at? The boat is 12 years old, has 344 hours on it, and is in near immaculate condition. Only problem that we've ever had with it was recently when the engine wouldn't idle, but we solved that by burning all of the old gas and filling it back up. Did you know gas only lasts around 30 days now?