Have noticed in recent outings that my port engine was running slightly warmer than my starboard engine. Last trip running the engine around 1500rpm everything appeared ok but on increasing rpm up to 3000 and after a couple of minutes the rubber end plate attached by two hose clamps to the rear of the heat exchange blew off resulting in the bildge filling with fresh and salt water. Had an engineer look at and he couldnt see any reason for this happening so put it back together after checking the heat exchanger. The same problem occurred again when doing a sea trial. Appears that the raw water system is being pressurised to dislodge the rubber end plate. Temperature of the engine is not excessive when this happens. Anyone have any ideas as the engineer is a bit mystified.