Hi Bill- I am on my way to the boat to do what you suggested. I like the idea of smearing grease around the cover which should help if there are air leaks. There is a vented loop from the output of the heat exchanger to the exhaust elbow. I have not checked that yet so will keep that in mind. Dave
David Knecht Emeritus Rear Commodore/Thames Yacht Club Emeritus Professor/University of Connecticut Basketball Capital of the World > On Jun 6, 2025, at 11:38 AM, Bill Coleman via CnC-List > <cnc-list@cnc-list.com> wrote: > > > > On Fri, Jun 6, 2025 at 11:28 AM Bill Coleman <colt...@gmail.com > <mailto:colt...@gmail.com>> wrote: >> Sorry for this redundant comment Dave, but to go over the sealing of the >> pump, I would remove the impeller, smear a bunch of either vaseline or >> silicone grease on the back and circumference and blades, push it on firmly, >> maybe put a straightedge across the face of it to make sure there is no >> space between the straightedge and the vanes. If your pump has a recessed >> gasket space or O ring so that the metal plate actually touches the edges of >> the pump, then there shouldn't be any space between the cover plate and the >> rubber vanes. If the gasket holds it away, then the vanes should be proud of >> the housing by that amount so the cover plate *just* contacts the vanes.. >> Then put more goop on the cover plate so you can create suction. In a >> perfect world, you would not need to do that, but . . >> Then check the hose coming out of the pump to see if the water comes out >> right after the pump. >> Also, Do you have a vented loop in that line anywhere, that might be >> something to check out. >> >> Bill Coleman >> Erie >> >> On Fri, Jun 6, 2025 at 8:21 AM David Knecht via CnC-List >> <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote: >>> As I always told my students, there are no bad questions or dumb questions >>> or insulting questions. Just questions. So I appreciate everyone trying >>> to help. It is why I love this community. Knowing you are all out there >>> gives me confidence to tackle problems that don't have YouTube videos to >>> walk me through. >>> >>> >>> To sum from some earlier questions: >>> 1. I verified that the pump shaft is turning. >>> 2. I am pretty sure the impeller is turning because the pump housing got >>> very hot very quickly from a brief test engine run with no water moving. >>> 3. I can find no obstructions to flow from the seacock to the pump. >>> >>> You comment actually makes me wonder if I have been working under some bad >>> assumptions in doing diagnostics. I had presumed that water would flow >>> rapidly into the raw water pump due to water pressure and the pump would >>> move it along. But as you pointed out, the pump is quite a bit higher than >>> the entry point, so maybe the pressure is fairly neutral there. If I open >>> the seacock, with the cover off the pump, should I see water flowing into >>> the pump? Does the pump simply move water that is already there due to >>> pressure flow, or does the pump actually draw the water into the >>> seacock/strainer by sucking it in? If the latter, then many of my tests >>> have been beside the point and nothing is blocking the flow of water into >>> the boat. It is more that the pump is not drawing the water in, which gets >>> back to the air leak issues mentioned. >>> >>> 1. If it is air leaks in the pump seal, I would propose to use a gasket >>> sealant line Form A Gasket in addition to the o ring to seal the cover? >>> Any reason that is a bad idea? >>> >>> 2. I asked earlier, but is there possibly a pump priming issue? I have >>> never heard of someone having to do anything to prime there raw water pump. >>> I did read an online engine thread where people had this problem with a >>> particular engine, but simply revving the engine got the pump primed and >>> pulling water. Dave >>> >>> David Knecht >>> S/V Aries >>> 1990 C&C 34+ >>> New London, CT >>> >>> > Your contributions help pay the fees associated with this list and help to > keep it active. Please help by making a small contribution using PayPal at: > https://www.paypal.com/paypalme/stumurray All contributions are greatly > appreciated.
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