Here you go. you don't want to run any wiring without one. It also makes for a super clean looking battery, With only two larger wires going to the battery. And not a rats nest of small wires all over the place. I run a lot of switches as you can see, and this set up is perfect for me www.jamestowndistributors.com/product/product-detail/11684
As WetWille stated, Velcro is a great tool. I never had the box come loose.
You can see the same fuse box under the dash in this picture.
Click the link below for information on vintage Mercury restorations
On my Vagabond II, I bought a marine type fuse box that has LED lights that illuminate should a fuse blow. I liked that idea because it'll make it a lot easier. I then glued industrial strength Velcro on the back side of it and a larger piece of the matching Velcro to the backside of the dash on the passenger's side. Then, I just stick the fuse box to the backside of the dash and take it down to look at while I'm seated if needed. Piece of cake.
It's very difficult to find much on these boats I find. I'd like to get notified if anyone responds to your topic. I've got to start on wiring a complete new set up as well but now sure where to install the main fuse Manuel. I was thinking underneath the bow somewhere which would be close to where the ignition lights and other accessories are located. I'll be nice to see some other photographs of what other people have done.