Re: Is it worth it? Rent vs. Own
Thats a tough question, and one probably only you can answer yourself...
You will have to figure out how often you plan on using the boat, and multiply that buy the cost to rent one. Obviously at some point if you are planning on doing this long term, eventually you will have spent enough on rental fees to have just bought something.
Things to consider:
Pros of renting:
Use it and go.. (Don't have to clean it, do the maintenance, store it, wax it, etc.)
Cons of renting: it's not yours, so your limited to using it only when you can rent one, availability of rental boats, ongoing costs of renting (plus 85 seems cheap, its 200+ to rent a boat for a day here).
Pros of owning:
Boat is yours, you can do what you want, when you want, and not have to worry about it. (thats the only real pro I can think of hehehe)
Cons of owning: You have to buy it, store it, maintain it, and fix it when stuff breaks, (and it will break).
Now for the specific boat you mentioned, being that old and needing a new deck, I would say you're looking at nothing shy of a total rebuild (deck, stringers, transom). On top of that the motor isn't even in running condition. That will be a major project, and you will never recoup the money you put into it.
Good points are, if you want something for the long term, you will have a nice solid boat that will last you for years. Bad points are, that old of a merc will need a bit of work to keep it going, plus the initial cost of getting it running. When considering the cost of a "project" boat, you have to figure the hull as "free" because they are worthless, (if junk, you even have to pay to dump em). So the only thing you are paying for is the motor/trailer... You could be in for a lot of cash from the get go between fixing up the motor, rebuilding the boat, and servicing the trailer. Is the motor and trailer worth the 250?
I would suggest reviewing the restoration forum, and really looking through some of the "total rebuild" threads so you have an idea of what you will be in for. If you think you're ok with the work, costs, and time, and want to own, then go for it.
If not, but you still really want to own, then buy a starter boat, keep shopping around... there are plenty of boats out there that would be water ready in the range of what you would spend to get another boat rebuilt...
Good luck