that code is for the raw water low flow. there is a paddlewheel sensor that screws into the intake pickup tube for the raw water. Pull the paddlewheel out (unscrew the circular piece holding it in then just pull the sensor out) and inspect for debris. Can also take a look at the underneath the boat at the raw water pickup.

Likely if your not overheating its not a true water flow issue, but better to check it out and be safe.