How acurate is NADA.com?

According to nada.com my 2003 Merc 9.9hp 2 stroke pull start is worth $780 and a 1998 Merc 25hp 2 stroke electric start is worth $720. Both prices are for average retail ( both motors are low hours, in mint condition ). How can the 25hp be worth less for only being 5 years older and electric start?

Looking at upgrading to another boat with the 25hp, and trying to make sure I am getting my money's worth.

I don't know about where you live but around here for used boat related stuff nada means nothing for the most part.
It all comes down to what a buyer is willing to give or a seller willing to let it go for.

The real question is. Is it worth it to you?

Exactly. The market sets the price, not any book. Same for cars and trucks. NADA says my Mustang is worth $3700. I had it for sale and couldn't get anyone to offer any more than $2000 due to the miles showing on the odometer (300,000+).

Locales are also a factor. Out here, you can't buy a 25 hp motor, short shaft of long, for less than $1500....and for $1500, you get don't usually get much. Mega 25's, Yamaha triples, Suzuki DT25's, and 3 cylinder 25 OMC's bring upward of $3500. More in some cases.

NADA is great if you're buying and terrible if you're selling. With that said, folks around here use Craigslist as a better indicator of the market...

NADA says my boat, motor and trailer, couple options are worth over $6k average retail. I don't think so, paid way less than that for it.
So like they all say, market price is king. I do believe though the cheapest way to buy a motor is to buy the boat and trailer along with it, especially if it is an old fiberglass tri hull or similar. Some people just want to get stuff off their property.
Tim