David:
Sorry for this unhelpful response, but I figured I’d pass along
my situation to add to the mix. Since I bought my boat, I’ve had a problem
getting the “siphon” (for lack of a better term) started for the engine raw
water intake. The boat goes in the water, I open the seacock for the raw water
intake, the water has no obstructions and easily runs through the strainer, but
when I connect the hose to the engine the water doesn’t circulate. Instead, I
must connect a separate hose with a funnel up on deck, pour water into the
funnel, get the “siphon” going using gravity, then quickly switch hoses. After
that, the water spits fine. In fact, it spits more powerfully than any boat
I’ve ever seen, so the impeller is not the issue. However, anytime the water
intake thru-hull is out of the water – even for an instant during rough weather
– the “siphon” is broken and I need to do the funnel routine to get it started.
We’ve looked at a lot of potential causes and have yet to figure it out. I’ll
be interested to learn what you discover.
Matt
C&C 42 Custom
From: David Knecht via CnC-List <cnc-list@cnc-list.com>
Sent: Thursday, June 5, 2025 10:16 PM
To: CnC CnC discussion list <cnc-list@cnc-list.com>
Cc: David Knecht <davidakne...@gmail.com>
Subject: Stus-List Re: Water pump mystery
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
On Jun 5, 2025, at 4:58 PM, rickbrass--- via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
At the risk of stating the obvious and being insulting, be sure the end of the
raw water inlet hose is well below the waterline level of the boat. If the open
end is too high, you would probably see only limited flow due to the reduced or
nonexistent pressure.
From: David Knecht via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> >
Sent: Thursday, June 5, 2025 4:42 PM
To: John Irvin <skis...@outlook.com <mailto:skis...@outlook.com> >
Cc: Stus-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> >; David
Knecht <davidakne...@gmail.com <mailto:davidakne...@gmail.com> >
Subject: Stus-List Re: Water pump mystery
Update. Diver confirmed nothing blocking thru hull. So with seacock open water
flows strongly out of strainer with lid removed. But it dribbles slowly out of
raw water pump inlet hose. The only thing in between is raw water strainer.
Basket is clean. Not sure how to assess water flow through it but suppose i
will have to remove it. Major inaccessible pita. Dave
Sent from my iPhone
On Jun 5, 2025, at 1:44 PM, John Irvin <skis...@outlook.com
<mailto:skis...@outlook.com> > wrote:
It’s more likely to suck air and not pump.
Get Outlook for iOS <https://aka.ms/o0ukef>
_____
From: David Knecht via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> >
Sent: Thursday, June 5, 2025 1:13:24 PM
To: Stus-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> >
Cc: David Knecht <davidakne...@gmail.com <mailto:davidakne...@gmail.com> >
Subject: Stus-List Re: Water pump mystery
Fyi. I am on my mooring so some ideas aren’t practical. Dave
Sent from my iPhone
On Jun 5, 2025, at 1:09 PM, David Knecht <davidakne...@gmail.com
<mailto:davidakne...@gmail.com> > wrote:
Hi john. Wouldn’t the pump be leaking water if seal is bad? Dave
Sent from my iPhone
On Jun 5, 2025, at 12:49 PM, John Irvin via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
Impeller gasket must make a perfect seal.
Get Outlook for iOS <https://aka.ms/o0ukef>
_____
From: ALAN BERGEN via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> >
Sent: Thursday, June 5, 2025 12:46:37 PM
To: Stus-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> >
Cc: ALAN BERGEN <trya...@alumni.usc.edu <mailto:trya...@alumni.usc.edu> >
Subject: Stus-List Re: Water pump mystery
Air might be getting in without water leaking. It happened to me once, and it
took me a while to figure it out.
Alan
On Thu, Jun 5, 2025 at 9:00 AM David Knecht via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
Hi alan. Wont it leak water if seal is not tight? I have new gaskets on order
but figured if it didn’t leak i was ok for now. Dave
Sent from my iPhone
On Jun 5, 2025, at 11:39 AM, ALAN BERGEN via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
If the cap on the raw water strainer doesn't have a tight seal, you won't get
water pumping.
Alan
On Thu, Jun 5, 2025 at 8:31 AM David Knecht via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
Eliminated many possibilities yesterday. Pump shaft turning fine. Replaced
impeller. Still not pumping water. Has anyone had a priming problem? My
current hypothesis is that either the pump is not self priming or the seacock
is partially plugged limiting flow. Water comes into raw water strainer with
lid off but no idea if it is normal rate or not. Dave
Sent from my iPhone
On May 30, 2025, at 9:39 PM, Ronald Scott via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
Possibly the impeller connection to the sea water pump pulley became
disconnected…resulting in the impeller not being turned to pump properly the
sea water. This happened to me when I had installed both a new seawater pump
and a new impeller. The guy doing the installation made the connection better
between the impeller and the sea water pump pulley, and normal pumping of water
resumed out the stern. He did say that the pulley was somewhat worn (where it
connects with the impeller), and suggested I install a new pulley. Hope this
helps!
Ron Scott
C&C 35 MK II (Rapid Transit)
Drayden, MD
Danville, Ky
Sent from my iPhone
On May 30, 2025, at 3:51 PM, ALAN BERGEN via CnC-List <cnc-list@cnc-list.com
<mailto:cnc-list@cnc-list.com> > wrote:
Is the belt tight enough? Run the engine and see whether the pump is turning.
If not, tighten the belt. If yes, remove the exit hose from the pump and see
whether water comes out when the engine is running and the pump is turning. If
no water comes out, change the impeller.
Alan Bergen
35 Mk III Thirsty
Rose City YC
Portland, OR
On Fri, May 30, 2025 at 12:34 PM David Knecht via CnC-List
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote:
I noticed today when i turned the engine on that i could not hear water coming
out the transom port. Just air bubbles. Also the temp gauge read zero which i
am guessing would happen with no water near sensor. Opened intake strainer cap
and water comes in when seacock is opened. Took cover off sherwood water pump
and looks normal inside. No missing vanes. Opened seacock and water came out of
hose from the intake. I’m stuck. Any ideas?
C&c 34+
Universal m4-30
Thanks.
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://urldefense.com/v3/__https://www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!pZPXqf0N06PSxGS6nGO9KrBafHmmNbAHvV1qXeoJBQtWUzsqpX0o7OHRecZKK1B_ilJoRZ2G7haKXPI9iCONU2g$
<https://urldefense.com/v3/__https:/www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!pZPXqf0N06PSxGS6nGO9KrBafHmmNbAHvV1qXeoJBQtWUzsqpX0o7OHRecZKK1B_ilJoRZ2G7haKXPI9iCONU2g$>
All contributions are greatly appreciated.
Your contributions help pay the fees associated with this list and help to keep
it active. Please help by making a small contribution using PayPal at:
https://www.paypal.com/paypalme/stumurray
<https://urldefense.com/v3/__https:/www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!qDCB107FV545ldgV0tlZsQBNKnpSYz9z0E9zQPRdIsNRWQRwwuSzb6re2jDKQW-KijaHYMyaCaM47J4ZkqHtOaQ$>
All contributions are greatly appreciated.
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://urldefense.com/v3/__https://www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!qDCB107FV545ldgV0tlZsQBNKnpSYz9z0E9zQPRdIsNRWQRwwuSzb6re2jDKQW-KijaHYMyaCaM47J4ZkqHtOaQ$
<https://urldefense.com/v3/__https:/www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!qDCB107FV545ldgV0tlZsQBNKnpSYz9z0E9zQPRdIsNRWQRwwuSzb6re2jDKQW-KijaHYMyaCaM47J4ZkqHtOaQ$>
All contributions are greatly appreciated.
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.
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>
https://www.paypal.com/paypalme/stumurray All contributions are greatly
appreciated.
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.
