Welcome to iboats Howard!<br /><br />Standard prop is a 9 1/4 X 10. But the more important questions is, what are you putting the 9.9 on? There are a few sizes available. And yes, the Sea Horse will use the same prop.
General usage props by OMC range from 91/4 X 8 to 9 X 11.Application and size and type of boat that the engine will be pushing will dicatate which pitch and style of prop is suited best.
