How to test a small engine ignition condenser?

Is there a way to test an ignition condenser to see if it is working properly? Aside from replacing I mean. The small engine is a 25 year old 2 hp Johnson outboard motor and the spark is strong but interrmittant with a spark tester. And what exactly does a condenser do? Is it like a capacitor? Can I put 2 in parallel? Would that help the spark quality?