I dynoed one of my engines before going into the boat. Ran great , A/F great , EGTs great. Now in the boat @ 3000 rpm my A/F meter is like , 10.9 and my plugs are getting crappy.
I guess my question is , because of the angle the engines on , should I adjust the float level a little on the low side , at least on the front side of the carb? I think I may be dumping some gas out of the boosters while running.

Make sure the floats are in the bottom of the sight glass with the boat in the water. Unless they were set real high I can't imagine a little more angle making too much diff.

My guess would be something related to a change in vacuum at that same RPM vs what the motor saw on the dyno. Depending how the dyno operator was loading the motor and how fast it went thru the RPM band usually increasing RPM's at 600/sec. I experienced something similar vs dyno except mine was going lean, for the same reason.