Have no fear!!!!! Money solves all problems and creates all evils!!!! If you are fastidious in your research, you will end up paying the same amout of money out of your pocket any way you go. The only difference is the rate that it leaves your pocket!!! Forget the engines for now. You will not be spending much time with them relative to overall time spent on the boat. Instead, find a boat that you want to stay on and with and over time you will solve the different problems that appear. i.e. quit standing at the end of the diving board and jump in. The board ain't so high. And boats are not like women, you can always sell the boat if you find you do not like it. Women are a little stickier.
Motors, used, are from 2500 up. Dollar variables are linked the exhaust replacement costs, rather than the costs of a short block because the blocks last so long. The exhausts do not. Sea water and all or fresh water. Installation is usually the same cost as the motor, that why so many of us DIY after renting the crane. Always lie to your mechanic about how much you paid for the engine. Instead, counter by asking him what he would have paid for them and then quickly change the subject before he has a chance to double what you paid.
Offer him a $1,000 each to do all the work. He will jump on it. Of course, $2,000 will put you through mechanics school, too...
Philosophically, you are always going to face issues, delimma, insolvable problems, or choosing between the lesser of two evils (which is where I started this lecture) with a boat. Work on getting the hull you want, like, or fall in love with, etc. then work on the lesser problems, like engines, steering, cosmetics, electronics, etc. Put out your own "wanted" ad for the kind of boat you want and quit the "endless search" unless you like to search.
If you like to search, come see me and I will sell you all 16 of my boats for $100,000 dollars and you can begin to search for places to get rid of them and really maximise your pleasure!!!