What are the chances of both engines failing?

Phil May and Andrea Twigg
Sat 21 Sep 2013 03:46
41:15.6N 72:28.8W
We left Mystic bound for Duck Island, a short hop along Long Island Sound.  As we were pulling away from the dock the port engine shut down with a loud beep and the “Check Engine” light flashing.  Fortunately there was not too much wind and we had enough clearance from the dock to pull away on just the starboard engine without being blown into anything.
Sometimes the engines shut down because if they are run slowly for long periods then the turbo blades get clogged with soot that needs to be burned off.  Our generator is out of action and we have been using the engines to charge the batteries, so sooting up seemed a likely cause. 
Motoring towards Duck Island I ran both engines at 3000 RPM for a while to see if it would clear the problem.  The port engine would run for a while but still shut down periodically.  It also seemed unwilling to rev very high, which is indicative of a blocked fuel filter.
Meanwhile, revving both the engines high made the starboard engine overheat and shut down.  We limped into Duck Island with just the one half-powered port engine and dropped anchor.
The port fuel filter was pretty dirty.  I replaced it and the port engine seems to run OK now. 
The starboard engine was completely out of coolant and attempting to refill the coolant tank was simply filling the bilge up with water.  Upon further inspection it turned out that the hose running from the engine to the hot water cylinder was draped through the bilge and it was completely rotted through after years of exposure to the oily bilge water. 
We replaced it with a spare piece of freshwater hose, just to get the starboard engine usable until we can get a proper replacement hose.
I guess the moral here is that if one engine is playing up you should be really gentle with the other one.
What bilge water will do to a coolant pipe