I Dissolved my Engine (Almost)

2 years ago I replaced the almost 40 year old Volvo Penta MD7A diesel engine on the boat for a 10 year old reconditioned Volvo Penta D1-20. I performed really well until what appeared a minor problem turned into a major part replacement. I believe it was caused by my silly use of cheaper non-Volvo coolant which didn't have the additives to minimise galvanic corrosion between the aluminium heat-exchanger and the steel engine block.
A costly mistake which I will not make again. The video charts all of the steps I took before discovering the problem - and the solution.