No cooling flow on F90TLRC; overheating and alarm

I just purchased a used pontoon boat with a Yahama F90TLRC (61P-L-1007213). The motor and boat were left in the water for years with little to no usage. I have removed and cleaned the 4 carbs to deal with fuel starvation. I hooked up the water ears and ran the motor for a bit. After hearing the warning tone, I powered down the motor and witnessed steam coming out the pilot hole.

I tried to hook up the garden hose to flush the cooling system but nothing appears to be flowing through the system. The fresh water lake where the boat was stored is high in calcium with lots of buildup on the toons. I'm wondering whether the buildup is also in the cooling system.

Any suggestions on what to do yet? I'm not clear whether it is a blockage, a pump or impeller issue. Please help!!

/jm

Re: No cooling flow on F90TLRC; overheating and alarm

Best to remove/inspect/replace entire water pump, check/replace thermostat and Pressure Control Valve. You need to do these items anyway, since you just purchased the boat and who knows if/when these routine maintenance procedures have been done. Don't want to overheat that motor! Good Luck!