Fresh water coolant loss when not running..?

[Chenega]

Hi,
On some Westerbeke models, the original Exhaust Manifold circa 1986 were subject to a recall. Might be worth checking your engine, Hansen Marine could tell you.

Well thanks Genkinyc! You were correct...
Not sure about the recall but I bit the bullet and replaced the exhaust manifold... no more coolant loss.
Exhaust gas check was okay...
Oil fine...
Pressure tests fine
Heat exchanger tested fine...
Hot water heater tested fine....

Thanks all for the suggestions