On Fri, Jun 6, 2025 at 11:28 AM Bill Coleman <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> 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 >> >> >>
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