Terry, I had a 23 I/O and had the switch mounted on the starboard transom between a hatch door and the engine cover. But I think something like the recessed battery switch box that Strick used on his 20 console would be real nice right below the SeaCraft logo on the engine box, or maybe forward and low on either side of the box. Short run to batteries and bus bars, not much movement and inconspicuous, but very accessible. Looking forward to mor pics of your 21.
http://www.classicseacraft.com/forum...&fpart=21&vc=1
