I have the same issue. DESS 204 470 771 was under water, and now same things. No DESS beep, no start and no gauges. Did it fix your problem? Because a new one is (Netherlands) 600 euro.
(2004 Sportster 4-tec Rotax 155 hp)
I have a Speedster 96. The portside motor starts in a second and then runs fine. It also accelerates like a rocket. Then after a 10 minutes the motor goes back from 7000 to 3000 rpm. When I push the throttle, it dies. When I pull the chocke, it also dies. Then a hard start and then it runs good...