The original bulbs were rated at 8 watt at 12 volts. There are two bulbs in the bow for the red and green navigation lights. Another one for the white stern light. If I ran the masthead light too, that was a total of 32 watts or about 2.67 amps.
The existing Perko running lights on the S2 6.9 use what is called a festoon bulb. They look like a barrel with the connections on each end. These existing 8 watt bulbs are about 1.25 inches long. Make sure you get the right size. You can go to any auto parts store and buy a pair for about $6-7 bucks.
I wanted to replace mine with LED lights so I went to my trusted source Amazon.com. I do all my shopping there. Sure enough, I came across some 1.25 inch (31mm) festoon LED dome light bulbs. These were even cheaper than the standard bulbs that I saw at the auto parts store. I purchased the four pack for $6.49 plus free shipping, what a deal! They have 12 LEDs so they very bright.
I could not find a wattage rating on the package so I do not know for sure how much energy they draw. It is probably in the range of a few watts a piece, significantly less than the 32 watts I was using. They are not marine rated so saltwater or moisture may affect them after a few years. At that price, I really don't care. They should last a very long time and save me many amp hours of battery use.
Pick some up yourself and get out and do some night sailing!