You can determine a reasonable asking price for a Boston Whaler MONTAUK 17 boat by looking at prices being asked by other sellers, by looking at prices paid by other buyers, and by looking at listings of other MONTAUK 17 boats offered for sale in the MARKETPLACE forum or on commercial used boat listing websites.
As you describe, the asking price for the MONTAUK 17 boat will be a sum of the values of all the various components involved in the boat. Typically the components are
--the hull
--the outboard engine
--the boat trailer
--any accessory gear included in the deal.
You have to assess the value of these four basic elements of the package, then sum them together to arrive at an asking price for the package. However, I would not expect that you could sum all the elements without having to apply a discount, that is, one often sees that when buying a package the total package value may be lower than the value of the individual components if those components were sold separately.
There are other factors that affect the value besides the actual physical components. These factors are:
--location of the boat package; prices vary in different regions
--the time of year; prices vary in different seasons
--general desirability for the particular size and model of Boston Whaler boat; some models are very highly sought
--general desirability for the particular brand, model, and technology of the outboard engine; some engines are very highly avoided
--general harmony of the combination of components; are all the elements properly suited for each other and in appropriate age, condition, and size or capacity.
The most influential factor is the physical condition of all the elements in the package, particularly the condition of the boat hull and all original components from the factory. There is a curious phenomenon in which sellers of boats in rather shoddy condition think there is little discount to be applied for this poor upkeep, and yet buyers often fail to realize the value inherent in a used boat in excellent condition and seek a discount.
Another significant factor is the age of all the physical components. Many classic Boston Whaler boats from the 1980's are now over 30-years-old, and one should not expect that they can retain a huge percentage of their original purchase price forever--unless the hull is in spectacularly good condition.
For further discussion of pricing of classic Boston Whaler boats, see
Buying Classic Boston Whaler Boatshttp://continuouswave.com/whaler/reference/buying.html