Craig,
I recently purchased a 17ft 1978 Boston Whaler Montauk with a 1978 Mercury 70hp and a 1988 Mercury 15hp kicker after months of search and research for a boat to fly fish Puget Sound from. After thorough examination and testing, my local marine mechanic reported that with proper care and maintenance, boat and motors should see a very long life. I’m saving the pennies, however, since the 70hp Mercury is the weak link in the system and will probably need to be replaced in some future year. Several things I learned along the way during my own search:
Age of a Whaler shouldn’t deter your purchase of one although condition of one should be a consideration. I’ve learned one needs very few skills to make quality, professional looking repairs and most repairs can be very inexpensive. The most important factor is to obtain proper guidance for the project at hand. My Montauk is now “near showroom” in appearance and I’ve invested less than $150 in materials and probably 15 hours personal labor to get it that way; it doesn’t look like the same boat we purchased and the price of it would have been a great deal more had the previous owner done to it what I did. The teak I restored now looks absolutely beautiful. I’ve never owned a boat before and my mechanical skills leave much to be desired.
Boston Whalers are known as the Unsinkable Legend. They will float level even when swamped and severely overloaded or even with large holes in the hull. This factor alone puts it into a class by itself; a true safety consideration other manufacturers can’t claim. The ride might be a bit rougher in 3-5 foot seas, but the boat’s lateral stability and invincibility far outweigh that for me. The USCG, U.S. Navy, DEA, FBI, U.S. Border Patrol as well as many local law enforcement agencies and fire and rescue units all use them. Must be a good reason for that. A good example of a Whaler's seaworthiness can be found by paging down to the photo on the following link: http://continuouswave.com/whaler/cetacea/cetaceaPage40.html ... Yeah, the ride can be a bit rough

;D
Those “blue books” that purport a boat’s value don’t really give an accurate picture of the vessel’s true market value though it may serve as a starting point. They list their values based on calculated depreciation from the original MSRP of the hull only. Many things affect a boat’s price such as onboard electronics, optional or additional equipment and intangibles such as varying demand in different areas of the country. Decide what you are willing to spend on a boat, be clear on what essentials should be included in that price and then search for one in your price range. http://boattraderonline.com/ is a good place to begin.
An entire community of Boston Whalers aficionados exists online at the Classic Whaler Forum http://continuouswave.com/whaler/ Many true industry experts here with an unbelievable wealth of knowledge in all aspects of Whaler ownership and operation (maintenance, repair, care, sources for parts, history etc.) If you were considering a Whaler, you would be remiss not to review the material contained there. The free exchange of quality information and advice from these folks has proven invaluable to me.
Whatever boat you eventually decide to purchase, I hope you get as much enjoyment and use out of it as I am from my Montauk.
Greg