We have an 06 300 in St. Petersburg. We had a flush out kit installed on both engines. We use Salt Away and the flush tool both can be bought at West Marine. Very simple process. Fill flush tool clear canister with Salt Away attach to hose and then snap on flush out tool to quick release on engine mounted flush kit. Turn on water, turn on engine. Canister will turn clear once the Salt Away has been injected. Turn off engine and water. For I/O's best to have boat raised on lift when flushing otherwise you are still flushing with salt water.
Best time to flush is when engines are still warm. Hope this helps.
