Hi, I had a similar problem on an early 300H, the model with a B&S engine and hand lever speed control. It started going slowly in reverse and eventually it would not reverse at all and the forward speed slowed to a crawl. I changed the hydraulic fluid first but this did not solve the problem and I thought the drive unit was shot. As a last resort I checked all of the linkages from the hand lever to the unit itself and found that the connection to the spindle on the unit was the problem. It is held in with a very thin pin which had almost sheared and the linkage connected to it was barely turning the spindle. I replaced the pin and the drive was as good as new. I may have just been lucky. These hydro units do fail, but it's worth a quick check of the linkage as above. If not . . . £700!!!!!!!!! Good luck.
Jonny, April 2009
