I have a 2002 LSV with the Indmar 310 with a carburetor. I have 180 hrs on the engine. My problem is a large loss of power. I can notice it in all conditions, but it stands out with a loaded boat. The engine used to perform great with a loaded boat, but now it struggles to get on plan. Any ideas were to start?

Oh yeh, I have had oil changes around every 50 hrs, but I have not changed the spark plugs. This is one place I was going to start.

Thanks!