I've learned there is really two types of dyno time: Working out the gremlins and actually being able to do the final tuning.

There are a select few places out there that have dynos and instrumentation that is really well calibrated enough to do the final tuning. This is even more so for boat motors as places that can run boat exhaust are few and far between.

Count yourself lucky that you were able to get all the gremlins out somewhere other than the middle of the lake, and do the final calibrations in the boat.