The other day we were out surfing and towards the end my boat began surging slightly while at a constant speed, fluctuating a few hundred RPM up and down at a pretty steady frequency. Almost seemed like it was running out of gas (it wasn't). I thought maybe it was PP related at first, and I don't remember now if I tried turning off the PP and going manual but pretty sure I did and it still did the same thing. I'm thinking possibly fuel filter, or God forbid a fuel pump. Anything else simple I'm overlooking that could cause this?