DZP1

Bought a 2007 SV240 last spring with 225 hours on it. Ran fine last year. Winterized (by marina) and in spring I replaced the cap, rotor, wires, plugs, fuel/water, fuel filter and oil/filter. Now this year there is this weird banging/flapping sound that occurs intermittently over 3500 RPM. The boat does have Sideswipe. Also, I removed the carpeted covers from the exhaust in the rear lockers. I'm half thinking this sound always happened and I just didn't hear it before. Anyhow, does anyone have any ideas or have you had this problem in the past? Video link below. It happens right at the beginning and then again at about 3-4 seconds and then throughout seemingly randomly. I tend to think it has something to do with the corsa sideswipe system, but cannot pinpoint it yet. Thank you for your help!