It’s well known that a boat with an inboard engine and a heat exchanger will need regular descaling. Any part of the engine that remains in constant contact with heated water will over time inevitably build up a layer of lime scale (calcium carbonate). For parts that do not get hot there is an added chance of encrusting organisms growing on the internal surfaces, including molluscs which build their shells in that same calcium carbonate. We have previously detailed the process of removing calcification in a heat exchanger for an inboard diesel engine (See Boating NZ, May 2022)
What is perhaps less well known is that outboard motors also suffer from this problem, especially if they sit unused for long periods. Scale may take longer to build up since the motors are usually lifted out the water and flushed with fresh water between uses,
