@uralite
First, your electrical issues:
IMHO, I wouldn't worry about the mess of wires. It is untidy but I've seen a lot worse posted on the forums. It's what's behind that real nice Blue Sea distribution panel where tidiness counts. That's where wires should be marked, bundled and secured prior going to the panel.
A few hours with some zip ties and that area can be made to look a lot better.
There is no need to start over or start diagraming your electrical system at this point. Untidy is not necessarily dangerous, just makes troubleshooting harder to do.
The issues I see that need to be addressed are:
1. All positive cables coming off the positive battery post need to be fused within 7" of the batter post. Easy fix. Install a MRBF (marine rated battery fuse) battery terminal fuse.Under $25.
2. Positive battery terminals need protective covers to prevent accidental shorts unless they are in covered battery boxes. The MRBF battery terminals will come with it's own cover. You will need a cover for the positive terminal itself.
3. Batteries need to be secured so they don't move. I doubt that yellow strap will hold them properly. You should add a properly secured strap with buckle to hold the batteries in place.
So you didn't check the water in your batteries. Your not the first and certainly won't be the last person to fail to do so. Replace the batteries and check the water monthly and fill as needed. Lesson learned.
BTW, it sounds like the batteries were doomed long before you got involved.
You can check the charger but it sounds like you already have identified what killed the batteries. A dumb charger is not necessarily dangerous to you. It will just shorten the life of the batteries.
I do agree with John on this point.
Perhaps before going any further and asking your friend for money to change the boat with this or that it would help both of you to open all of the cabinets and reduce the “OMG” drama to a list of all the items you see. Your own survey of the boat and all of it’s systems.
Then begin your list making using categories: Propulsion, Electrical etc. Then prioritize the list of things beginning with 1. SAFETY, 2. Things that need to be done, 3. Things I would like to do, 4 Things I’ll do when I get around to it. That way you and the boat owner can agree on what needs to be solved and what you want to solve. No more shocks “you need to spend another $1000 bucks on the boat right now or we are going to die.”
This is what I did when I bought my O'day 25 and again when I bought my C30. I found it very valuable to keep me on track and budget with my various repair and upgrade projects.
The photo of the wiring under the quarter berth doesn't scare me. I don't know what the standards are for that type of install but in my engine compartment I have many wires in close proximity of fuel lines, filter and pump.
I would move that grill gas bottle out of the cabin. They frequently leak. I don't store them in the boat, only bring them on board when I'm going to use them. I plan on removing the propane bottle for the stove/oven and store my grill bottles in the propane locker.