You didn't connect a toilet designed to pull in sea water to your fresh water system I hope...that's a major no-no and every toilet mfr specifically warns against it in their installation
instructions because it can't be done without risk of contaminating the fresh water supply, damage to the toilet pump or both. Only toilets that are designed by the mfr to use pressurized flush water should ever be connected to any fresh water plumbing
As to your problem...you're experiencing one of the reasons why it's a bad idea to connect a toilet that's designed to PULL water in to a water source that PUSHES water to it. It will not cure itself.
The right solution would be connect the toilet to a thru-hull as it's designed be installed. But since I'd bet real money
that you aren't about to do that, the fix is the same vented loop with an electric
solenoid valve that would be necessary if it were connected to a thru-hull. You'll find the instructions for doing that in the installation
instructions for you toilet model--which I'm guessing is prob'ly a 37245--that you can download from here: Jabsco > ITT Flow Control - Engineered for life.