I have a new Autohelm 1000 but no motor/battery on my sailboat. Can I use a 12v compact rechargable lithium ion battery and, is so, do I need any special hookup beyond connecting a positive and ground wire. I sail on a lake and would need no more that 4 hours of battery life before re-charging.

They take about 1 amp, so you'll need a battery with several amp/hours.
I have a 12v 9a/h lead acid battery which I often use for my diesel heater (electronics & blower fan), and as a back up. A li-ion battery should do the same trick.

A Wee Lithium - 9AH - for $70+ would be best option,as can carry the draw,and easily recharged .

Wary of powerpacks for continuous discharge/draw .

Have 25AH Lithium Battery,with circuit breaker, in plastic toolbox,with andersen plugs,to run Autohelm+Mini Watersnake on Tender .

Splash Proof ?

I've run an Autohelm on a small 12v lithium pack before and it worked fine just make sure the battery has enough amp hours for the time you'll be out.