If you had $1000 would you rather buy a fishfinder or acetone and rubber gloves? I'm busting your balls, but seriously think hard about this . . . you'll be in 15k with used power. I'm gonna enjoy watching this project and I promise not to say "I told you so".
4K in materials EZ . . . just to finish the boat on the cheap (not including rigging, new trailer, fuel tank, hoses, wiring, plumbing, electronics, batteries, bracket and power).