Re: 14' Seamor Marine-9.9 Johnson Planing Problems
Rather common problem with inflatables. Most models require a short shaft outboard but then tend to cavitate a lot. Try tilting the outboard before adding the planning plates as they require drilling.
When I run mine with a 9.8 long shaft, cavitation was never an issue. Now with the 15 HP short shaft I need to be wary of tilting all the time.