It's nice to see other people mentioning a VSR. I've had one fitted to the 90 for about 3 years now, and it works faultlessly. I don't reckon they'd like a winch, or work well with one, but that's no bother here .
Like Matt said, you could wire it with an 'overide' switch for jump starting yourself, if you wanted that ability at the flick of a switch, the few times i've needed to do that i've just swapped the leads over on the batteries. Other than that, a VSR just gets on and does it job.
Unlike a 'dumb' relay, a VSR won't close until the engine battery is charged, which is a good thing.
no stupid LED bar graphs
no current drain when the engine is off (ok, mA, just enough to run a chip)
easy wiring - a high current wire to each battery +ve, and a small earth. that's it.
the BEP marine unit is potted, so 100% waterproof, mine's been waded and is fine.