Generally speaking, low voltage DC solenoids don't have an overly restrictive contact voltage rating, just a current rating, at least over the range from a few volts up to maybe 80 to 100V. Contacts generally don't care too much about the voltage they are switching in this range, it's the current rating that matters.
The coil voltage is a different matter, as over-running that could cause it to burn out. However, most solenoid manufacturers offer a range of coil voltages so that they can be used with pretty much any system.
The reversing solenoid should have an option to allow the motor to run in one direction without the coil being energised if it is a true single coil, double pole, double throw, type, so that it only draws extra power when switched to astern. Some may work as you suggest, with one coil energised for ahead and another energised for astern. The ones I've used have always just had a single coil though.
This link to the Curtis Instruments contactor page may help: http://curtisinstruments.com/index.cfm?fuseaction=cProducts.DcContactors
For a permanent magnet DC motor where the coil is only activated when going astern you need a single coil, double pole, double throw, contactor, like the SW121 on the Curtis website: http://curtisinstruments.com/index.cfm?fuseaction=cProducts.DownloadPDF&file=50162%5FSW120DP%5FAlbright%5FRevA%2Epdf
Jeremy
--- In electricboats@yahoogroups.com, Bruce Gillett <affordableacadia@...> wrote:
>
> I see a problem with this solenoid. It's rated at 12 V (I assume for the
> coil, but maybe for the contactor too?) Even if it's good for 36 V., what
> about the common ground? I would be using two power supplies and don't plan
> on connecting their grounds. Also, this is unclear whether one coil would be
> "on" during forward. Others like it are. I have found another solution, the
> Cole Hersee 24400. I would have to use two, but both would be off during
> forward. Unfortunately, it's a steel case. Not good for marine. Also, should
> one fail I would blow a big fuse pretty quickly.
>
> On Sat, Sep 3, 2011 at 3:33 AM, Jeremy <jeremy_harris_uk@...> wrote:
>
> > **
> >
> >
> > Bruce, here's a link for your side of the Atlantic, with a wiring diagram
> > that may be useful:
> > http://www.texasindustrialelectric.com/relays_24450.asp
> >
> > If you can locate a golf cart service place nearby you'll almost certainly
> > be able to pick one up there, as the majority of golf carts have them, I
> > believe.
> >
> > Jeremy
> >
> >
> > --- In electricboats@yahoogroups.com, Bruce Gillett <affordableacadia@>
> > wrote:
> > >
> > > Thanks Jeremy,
> > >
> > > I don't know why I couldn't find one in all my searching. Maybe I had to
> > > cross the pond? Anyway, even if I have to get it from the UK is seems to
> > be
> > > just what I need. Bruce
> > >
> > >
> > >
> >
> >
> >
>
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