Many bits and pieces to cooling systems
My first though, Phil, was that it was a blockage in your HX inlet port, but then realized your Yanmars are different than our Universal "bolted on" external HXs because we Universal guys have "marinized" tractor engines!
While not specifically an impeller story, this is one of our experiences that may help someone in the future, kinda related to Tim's reply:
Among the interesting little “tidbits” of information that I’d remembered reading about on the C34 website had to do with cleaning out the raw water intake with a dinghy foot pump. On a nice mid-winter March sail with Ken Heyman, our treasurer who was here visiting, we had just left the South Beach Marina and were motoring over to see the “Lady Washington,” one of the tallships that regularly visits the Bay Area and has cannonball encounters of the close kind with fellow tallships. Since it was cold out, there seemed to be a bit more white smoke from the exhaust than usual, which I attributed to the lower air temperature. Upon checking the temperature gauge, we noted it was pegged and stopped the engine immediately. Ken and I went through a checklist of actions we could take. Sailing back to the marina was not among them, since there was no wind and the end of the ebb was setting us north towards the Bay Bridge. Thru hull strainer clear – check. Raw water entering – check, but a trickle and less than expected. Raw water pump impeller in one piece – check. Raw water pump turning – check. Spare raw water pump gasket to replace cover – check. Temperature gauge working properly – check. Hoses and thru hull clear – hmm… We got the dinghy foot pump out from the lazarette, replaced the strainer and opened the seacock. Because the arrangement of the hoses and the strainer on “Aquavite” aren’t configured to connect the pump there, we removed the hose from the raw water pump and used the dinghy pump at that end of the hose. That turned out to be actually be easier than trying to work under the head sink. There was significant resistance at first, but after setting the three way valve on the foot pump to a higher pressure setting, the pump started working. Whatever had been clogging either the thru hull or the line was flushed out. Once everything was reassembled, we started the engine and all was well. Lesson Learned: It pays to read the material on the website because you just never know when you’ll be faced with an insurmountable problem only to find out that one of our skippers had “been there – done that” and had most importantly reported it for all of us to know. Thanks to Ken for his analytical assistance!
