Idling Rough - Any Ideas?

I have a 2000 MC X-5 with 470hrs on it. Bought it back in January with 400hrs on it. Everything has been fine up until a couple of weeks ago. Boat is starting to progressively idle rougher and rougher each time out. When sitting in neutral changing out riders, the engine fluctates up and down probably 250-300 rpms (tach moves back and forth) and when in gear coming back to pick up riders, I can notice it too. Also feels like there is a little bit loss of power and at slow speeds can hear a slight metallic pinging noise and an unusual rumble. Feels kind of similar to when you have fouled up spark plugs in your car and you notice loss of power on hills and it seems to surge when the engine is under load.

Any ideas on what this could be would be very helpful. Possibilities I think could be fuel filter or fuel pump, but I'm not sure. Also might need new spark plugs and/or a tuneup. Thanks.