Hi Ronan,
The exhaust on the D1-30 is subject to corrotion. Mine lasted for 14 years before it started to leak and I needed to replace both exhaust manifold and the exhaust bend. The local yard said that in their experience this is a common problem with the D1 – 30 engine. However the water involved is of course salt – unless you are in an inland lake of course.
Good luck
Scott Millar