Spares to keep on the boat

I just bought a 1994 Grady White Express 20 with a 175 Yamaha Saltwater Series Outboard with low hours. I was wondering if anybody had any suggestions on what spares I might want to have on board. I don't have a lot of room and I don't want to add a lot weight but I would like some ideas of some basic parts that I might get caught replacing offshore in a pinch. What kind of spares do you guys like to carry? Any special tools that are helpfull?
Thanks for your suggestions, Tom.

Make sure you have a tool kit...Metric! Also, I store all my filters in large zip lock bags...this will keep moisture away from them

Spark Plugs

I find that it is best to pre-gap the spark plugs and leave them in the box inside a ziplock bag. Another good thing to carry is a solar battery charger in case of a discharged battery.

[mokaction]

Also one of those spare battery back up starter batteries packs. They are great in a jam..

Larry