Should shave added rpm went back up to 5900,Thanks for all the advice on this, wanted to report back on the cause of the problem. I had a recent tune up on the engine and went back to explore the low RPM issue, I pulled all the spark plugs and 5 of the 6 looked normal for plugs with ~10 hours. The 6th plugged looked brand new and had no signs of having ever fired. I replaced all the plugs and the boat is back to normal. Thanks again!