...what would be involved in changing the 32v electrical system on an older Roamer to a more modern 12/24v system?
Only money. My guess would be a total rewiring. Cost me $3500 to rewire the 110 AC system - five years ago. Money well spent. See here: http://www.geocities.com/tin_tonic/ElectricAvenue.html
I'm not sure you'd have to rewire the entire boat; I suppose it depends on the condition of the wire and the current you're pulling through it to certain things. A few things you'll have to change to make work with 24 (not necessarily replace, but at least modify): - Starters - Batteries - Alternators - Light bulbs - Bilge pumps (although these would probably be fine dropping the voltage some) - Battery chargers - Water pumps - Toilet components There's more also, I'm sure. It wouldn't be a small task. Is the 32 creating a big problem for you?
