The Rotax jet drive engine is cooled via a closed-loop system with antifreeze, which circulates through cooling plates on the bottom of the boat, while the “carbon seal”, which seals your driveshaft, is cooled by direct contact with water. Additionally, raw water is pumped in and cools the exhausts, and intercooler, so the answer is yes, you can run it out of water, but not for a lengthy period of time, and you should only idle the engine, not rev it up.
If you have a water hose attached to your flush port, that will cool the exhaust, but the cooling plates are still exposed, and the carbon-seal is not being cooled, that will be your limiting factor.
You will see a lot of different opinions on this, but after extensive research, we have noted that about 2 minutes is the max you should run the engine out of water, with water attached and running to the exhaust, with engines idling. Again, do NOT rev the engines, this will heat up the carbon-seal quickly, and can overheat and ruin it.
It is OK to quickly blip the throttle up to 4500, after turning off the water, to clear it out, if you wish, but then kill engines immediately.
A related question is how do I hook up water to flush out my engine? There is a port on the upper left rear of the jet drive where a standard water hose can attach, that allows running water through the exhaust cooling path for flushing or cooling.
You may attach a hose here to flush after running in Saltwater, or to allow you to idle your engine while out of water, but it is VERY important you follow the correct order of turning on the water, as follows:
- Engine Start.
- Water on.
- Water off.
- Engine off.
The water must never be running when the engine is not, because it would be possible for water to be forced into the exhaust ports of the engine, possibly hydrolocking it, and causing damage.
Again, engine on, water on, water off, engine off. Engine can be run up to about two minutes max doing this, idling, but do not run it longer than necessary, and if you run it two minutes, you will have to let everything fully cool down before attempting it again.
It’s best to run it as little as possible out of water.