Its a 17 Helix. I upgraded the rear ballast to 1190's and ended up going with an Acme 2079 prop because of the weight and altitude (7500'). Boat runs great, surfs great... but when I pull the kids on the tube (obviously no ballast), I can feel a random vibration or slight growl from the driveline. I pulled the boat several times, checked the prop, nothing.

Yesterday I loaded the boat with extra ballast in the floor using a stock bag (750?) and while surfing, the vibration came back again. Very random, no rhythm to it so I could not track it... no specific speed, happened on both goofy and regular waves... Is this all a weight thing? I would think that boat could handle the weight and the wave was really good so I was hoping to try it again. But I ended up draining it all and of course no vibration.

Any suggestions on what to check next? I had it at the shop for service before season, and they did not find anything. I live 3.5 hours from the dealer, so I am hoping to not have the boat out of the water for a few weeks.

TIA