Re: Just buy a boat already....
there's a time/value aspect of the old boat/cheap boat and DYI other than your time doing the fixing, and that's loss of time on the water due to repairs (which is why, if you must have old boats, have three, so one will be running).
Let's say you live up north and have children in school so your boating season is Memorial Day-Labor Day plus a few weeks on the shoulders, and you are a "weekend family boater." That's about 18 weekends. Scratch 6 due to other obligations, 12 weekends=24 boat days. Knock off 6 for rain/wind. 18 boat days. (It never rains on the weekends when you wouldn't be boating anyway--that a law of nature).
You find a problem Friday night while prepping, cancel the trip, Take it to the mechanic, wait two weeks. Now you have 14 boat days left--but if you have an old boat, it will happen again during the summer.
Or fix it yuorself, but being busy, it may take you a week or two to diagnose, get parts (order online?) get around to fixing, consult iboats, fix again, test.
Worse, arrive at the lake, encounter problem, cancel trip, return home--too late to get the parts to fix it this weekend. Maybe two weekends from now you'll be back at the lake--oops, that's your parent's anniversary picnic, or when you are helping daughter move, whatever.
So 14 boat days out of 365; 2 weeks out of 52. Get your annual cost to own and run, add $800/year repairs, divide the purchase price by 5 (my guess is avg life of used boat is 5 years before you sell it. OK maybe 10.) If it's $4000, it costs you $2000 a week to boat.
Now you might risk $2000 to go to Disneyworld b/c it isn't likely it will be "broke down" when you get there (Hurricanes?) Little risk of wasting your money, and there's trip insurance. Buy a better boat, and you help cover the risk that your annual investment will not be wasted. As much.
So when someone considers buying an old cheap v reliable expensive, they have to take a good hard look at how "break down tolerant" their boating style is. A boat down for a couple weeks is effectively down for the year for many people. Also why you get them running early.