New poster here. I have a early model 743. The Hyd. warning light comes on after 20-30 minutes of running if I have the throttle higher than half-speed. I think it is because of temperature and not pressure because it is not intermittent. It will only go off if I reduce throttle or shut the engine down and wait a while. If I work at less than half throttle, I can go for an hour or more without the light coming on. Engine temp seems fine and doesn't get much over 150 on the gauge. I had the motor replaced last year and the radiator checked at the same time. I just had the unit into the shop because of cavitation and they replaced the hydostatic pump, checked all the seals, etc but found no source for the air in the system. I did not have this problem before it went in. I have checked hyd. oil level (has the two petcocks on side of resevoir) & replaced the filter. The hyd hoses feel very hot but I don't know what is normal. Any ideas on what to check next would be greatly appreciated.