for the record, i was not suggesting anyone run lower octane than recommended by the engine mfr; all i'm saying is it is possible to run safely with proper tuning, which may not be feasible on a boat motor.
i've talked with Indmar before about PCM programming software, and IIRC it would've been around a grand to get set up to tinker.
also for the record, i'm not suggesting tinkering unless you know what you're doing.