If you link two 6v bulbs in series this gives you 12v requirement. May i suggest using LEDs? This has been covered on other threads. With the appropiate resistor you can use 6v or 12v. Or any other voltage. Most bow thrusters use 7.2v.Again this has been covered before. I run my thruster off 12v but am careful not to run it to fast the imprellor can come off. John.