Yamaha waverunner question (temperature sensor)?

[Gliders R Awesome!]

I have a 1988 Yamaha 500 waverunner. When i start it up it starts up good but when running it flat out it only goes about 10mph... I put new fuel in it and no change. We just checked the temperature senson because it seems like the rev limiter is kicking in (but the engine isn't over heating) and got an opened circuit.

Does anyone know if the sensor is supposed to normally show an opened circuit or closed circuit???

Thanks!!