Hah! Another mariner! Just had to replace the front casting of our Volvo Penta 3 cylinder diesel. Corrosion due to suspected electrolytic action and the aluminium cover acting as a bloody expensive anode!
The only idea that I can offer is to check that engine has an earth strap. Other than that, is it possible that the engine has been run for a long time without anti-freeze or an anti-corrosion additive? I can understand that anti-freeze may not be necessary due to the higher ambient temperature. Is the lack of the radiator mounting bobbins an indication of unsympathetic maintenance?
