Cavitation I Think.

[David grant]

I have an 18 foot trailer sailer,with a 8 H.P. yamaha outboard.Great little motor pushes the boat ahead at a good speed against strong currents and wind,but trying to go astern even when going ahead slowly is quite hopeless,makes it very difficult when trying to dock at jetties etc.The prop is a high thrust type 9 by 7. I am only guessing at a possible cavitation problem.age of motor 1990+ model 8 C.M. I have seen on a mercury motor a sliding prop arrangement ,so when reverse is engaged prop slides back blocking off the exhaust gases, and reversing the flow. From enquiries i have made Yamaha do not make anything similar.Any help on fixing this problem would be greatly appreciated. Thanks. Granty..

[boats.net]

No I'm not aware of any kind of sliding prop available for it by Yamaha or any aftermarket companys. Maybe someone else here can give you more information.