Originally Posted by ancora
Took the boat our Friday morning to run the measured mile as we had a Predicted Log contest on the next day. With the Sicilian at the helm and me holding the stop watch we completed the first leg. Turned around for the second leg and the high water alarm went off. It stopped almost immediately, so I thought it was just a glitch. Finished the run and returned to our slip. While tying up the boat, we noticed the bilge pump putting out a good stream of water. The engines were still running so I opened up a hatch and found that the rubber end cap had come loose from the heat exchanger and was spewing water. Shut down the engines and put the boot back where it belonged. The hose clamps were original non-perforated painted green VOLVO. I'm guessing they just got loose a bit. Ran the contest today with nothing untoward happening. Just glad it happened on Friday, rather than race day.
My boat originally had a pair of those engines The bad design of the heat exchangers, using those rubber end caps, was the only thing wrong with those engines. What occurred on mine, (and had occurred before I got the boat, enough times that there were a pair of new rubber end caps in the spares box), was distortion of the end caps, not designed for the amount of water pressure within them, to the point that the brass separator in the heat exchanger, the one that is supposed to seat in between two pieces of rubber, would be out of its seat and the cooling water would bypass the heat exchanger and flow immediately out the exit pipe without cooling the engine coolant. I re-powered with TAMD41s, and haven'y looked back.
To reduce water pressure within the end caps, check for bits of zincs and impeller rubber in the HEs and in the transmission coolers.
For a permanent fix, you should be able to update your HEs to the 41s style and eliminate those rubber end caps.