Cavitation issues need help

[Irishtwins]

Ok I am new to this forum. I just purchased a 98 seagull 19' catamaran(new to Cats) with a 98 70hp Yamaha I have put a hydrofoil on the motor and it helped eliminate a lot of cavitation but I still have cavitation during the holeshot. I don't have any pix of the set up but can get some. I have heard that the water level on a Cat is lower in the center. I am trying to improve the overall performance of the boat and motor. Any help would be very well received. Thanks guys

 

[SkiDad]

If your prop isn't cupped then switching to a cupped prop should help with your ventilation issues. You could also try lowering the engine one hole.

 

[Sea Rider]

Your OB seems to sit too high on transom, Yam OB's likes to sit at a height for water flow at plane to pass slight under upper water deflector plate, if flow passes round AV plate will experience ventilation, worst at close turns at speed. If hydrofoil does not ride parallel to water level when combo is on plane, will achieve excessive water drag on hydrofoil that will slow combo down a bit.

Happy Boating