Strange DF40 problem?

[danncus]

Testing on a lake this morning for 40 mins. All ran very well until the last 5 mins. Cruising at about 4000 rpm steady throttle, revs went up to about 6000 and boat seemed to slow slightly. I stopped put it in neutral and set off as normal. I had to get the boat out at this point. The best way to describe would be like clutch slip in a car.
Any thoughts ?
Thanks

[catacom225]

Sounds like you have spun the prop bush

[JTNail]

I have had the same phenomon last season some times also. Until now I thought the propeller was catching air or something. But maybe I also spun the prop bush. I will try an new one soon.