Trap for young players

[briesey]

Recently I was undertaking some work on my hot water service which saw me removing the tank isolating the coolants lines from the engines via the valves fitted before the hot water tank, there is a the tee piece before the valves so the coolant runs and circulates without compromising the coolant system, I ran the engine and looked for leaks and all okay. Set out for a sail the next day and the alarm went off indicating the motor was getting hot, I shut down and sailed back to the pen only running the engine for a short time and by this time it had cooled down so no alarm. I looked hard for any leaks around the engine but could not see a trace until I pumped the bilge only to see green water pumping out the back, poured two lt. of water in the engine and ran it up, no leaks so checked the valves and no leaks, I then ran the engine above idle and there it was, coolant bypassing the valves...geez. The lesson here is do not rely on one isolation particularly a valve, plug the thread in the valve and make sure it's not leaking!