Used to be you could tell the different types of antifreeze by the color.
Can't do that any more.
Many of the newer aluminum engines need antifreeze that is silicate and borate free.
Find out what Westerbeke
says (it is not in the manual for the 30 B three) and let us know please.
They definitely say not to mix different types as a percipitate can form that can be damaging.
This sounds like you have a percipitate.
Get the right stuff and do a complete exchange. Not easy if you have a water heater
in the system that is lower than the engine.