The inlet for the fill pump is on the transom. When you put the boat in gear to move forward, the transom begins to not have water available for that inlet. The fill pump is not expected to work at any time except when the boat is floating and not underway. By attempting to run it when it isn't going to work, you're sucking air into the system and creating a bubble even bigger than if the pump plumbing simply drained.
When you're going to be underway, the boat manufacturer expects you to turn off the fill pump and instead use the recirculating pump. You need to read the boat owner's manual. From your description, your problem appears to be operator error and unrealistic expectation, not an equipment malfunction. There are some saltwater boats that have a scoop mechanism to get seawater when the boat is underway, but I've never seen this as a factory feature on a bass boat. Such a mechanism would have considerable issues with vegetation clogging in freshwater environments.
Its not a bass boat.
There isnt a recirc pump, it has a gravity oveflow drain above the waterline, its a one pump setup. It worked before at idle speeds, now it doesnt.
I dont need to read the manual thanks anyway, save that remark. I do all my own work.
Its getting air in it that wont get out even with the boat is stopped. It doesnt work even at low idle, I know it doesn't work on plane never expected it too.The pump works once and a while, off and on sometimes gets it going. I pulled the hose and made sure it actually is pumping works fine with the hose off.