The cooling system on my sailboat diesel engine has raw seawater
passing through a heat exchanger to cool the coolant. Here is the
flow path.
Seacock-hose-raw water strainer-hose-water pump - hose-heat exchanger

For some reason it does not want to pump and is acting like a pump
losing prime. The hose from the strainer to pump is clear so I can
see the water beginning to flow but it will not make it to the pump.
I have verified that there is no blockage because i can blow through
from the water pump outlet hose all the way through.
When I put the clear hose going to the water pump directly in a
container of water, I get flow and suction and pumping after I prime
it. When I go through the strainer, I get less suction and less
pumpingafter priming but this priming is more difficult. Priming from
the seacock is very difficult and I let in a lot of air when I do but
this really should not matter, eventually it should suck up water.
But it doesnt.

Pumping from the seacock, I am surprised at the amount of air going
through the system.

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

wrote in message
...
The cooling system on my sailboat diesel engine has raw seawater
passing through a heat exchanger to cool the coolant. Here is the
flow path.
Seacock-hose-raw water strainer-hose-water pump - hose-heat exchanger

For some reason it does not want to pump and is acting like a pump
losing prime. The hose from the strainer to pump is clear so I can
see the water beginning to flow but it will not make it to the pump.
I have verified that there is no blockage because i can blow through
from the water pump outlet hose all the way through.
When I put the clear hose going to the water pump directly in a
container of water, I get flow and suction and pumping after I prime
it. When I go through the strainer, I get less suction and less
pumpingafter priming but this priming is more difficult. Priming from
the seacock is very difficult and I let in a lot of air when I do but
this really should not matter, eventually it should suck up water.
But it doesnt.

Pumping from the seacock, I am surprised at the amount of air going
through the system.

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Yes. Your pump is sucking air, Either a hose connection is not tight enough,
The strainer is letting air in, or a hose is leaking. Another possibility is
the pump. Bad shaft seal, impeller, cover gasket.

BTW We camped across the bay from Dog Island last night. That whole area up
there is lost in time.

On Oct 5, 8:40 pm, "Robert Jones" wrote:
wrote in message

...



The cooling system on my sailboat diesel engine has raw seawater
passing through a heat exchanger to cool the coolant. Here is the
flow path.
Seacock-hose-raw water strainer-hose-water pump - hose-heat exchanger

For some reason it does not want to pump and is acting like a pump
losing prime. The hose from the strainer to pump is clear so I can
see the water beginning to flow but it will not make it to the pump.
I have verified that there is no blockage because i can blow through
from the water pump outlet hose all the way through.
When I put the clear hose going to the water pump directly in a
container of water, I get flow and suction and pumping after I prime
it. When I go through the strainer, I get less suction and less
pumpingafter priming but this priming is more difficult. Priming from
the seacock is very difficult and I let in a lot of air when I do but
this really should not matter, eventually it should suck up water.
But it doesnt.

Pumping from the seacock, I am surprised at the amount of air going
through the system.

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Yes. Your pump is sucking air, Either a hose connection is not tight enough,
The strainer is letting air in, or a hose is leaking. Another possibility is
the pump. Bad shaft seal, impeller, cover gasket.

BTW We camped across the bay from Dog Island last night. That whole area up
there is lost in time.

Yes, there is an RV campground in St Theresa, I forget the name of
it. My boat is a little further east at Shell Point.

On Sun, 5 Oct 2008 17:17:37 -0700 (PDT),
wrote:

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Possible causes, more or less in order of likleyhood:

1. Raw water impeller is tired and needs to be replaced.

2. Raw water intake through hull fitting is fouled. I once sucked
in a jelly fish. Barnacle growth is common.

On Oct 5, 9:46 pm, Wayne.B wrote:
On Sun, 5 Oct 2008 17:17:37 -0700 (PDT),
wrote:

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Possible causes, more or less in order of likleyhood:

1. Raw water impeller is tired and needs to be replaced.

2. Raw water intake through hull fitting is fouled. I once sucked
in a jelly fish. Barnacle growth is common.

New impeller. Recent bottom paint and defouling. Besides, I can blow
down through the raw water seacock (with effort, it is 1' under
water).

In spite of all the hassle this has caused, it is fortuitous. While
working on the water pump, i saw a big nut under the prop shaft, then
a big bolt, couldnt figger out where they came from. The another,
HUH? I looked all over for their source. Finally noticed he prop
shaft and transmission were slightly misaligned. AHA, HOLY Shi%. My
prop shaft is held by only one bolt to the transmission output and
even that is coming out. This coulda been a truly nasty surprise when
waaaaay out in the Gulf.

It sounds like maybe it is sucking air. Check the lines coming into it.
If is worked before then perhaps someone sold you the wrong impeller. Do
you still have the old one?

wrote in message
...
On Oct 5, 9:46 pm, Wayne.B wrote:
On Sun, 5 Oct 2008 17:17:37 -0700 (PDT),
wrote:

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Possible causes, more or less in order of likleyhood:

1. Raw water impeller is tired and needs to be replaced.

2. Raw water intake through hull fitting is fouled. I once sucked
in a jelly fish. Barnacle growth is common.

New impeller. Recent bottom paint and defouling. Besides, I can blow
down through the raw water seacock (with effort, it is 1' under
water).

In spite of all the hassle this has caused, it is fortuitous. While
working on the water pump, i saw a big nut under the prop shaft, then
a big bolt, couldnt figger out where they came from. The another,
HUH? I looked all over for their source. Finally noticed he prop
shaft and transmission were slightly misaligned. AHA, HOLY Shi%. My
prop shaft is held by only one bolt to the transmission output and
even that is coming out. This coulda been a truly nasty surprise when
waaaaay out in the Gulf.

On Sun, 5 Oct 2008 19:16:09 -0700 (PDT),
wrote:

On Oct 5, 9:46 pm, Wayne.B wrote:
On Sun, 5 Oct 2008 17:17:37 -0700 (PDT),
wrote:

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. Any thoughts?

Possible causes, more or less in order of likleyhood:

1. Raw water impeller is tired and needs to be replaced.

2. Raw water intake through hull fitting is fouled. I once sucked
in a jelly fish. Barnacle growth is common.

New impeller. Recent bottom paint and defouling. Besides, I can blow
down through the raw water seacock (with effort, it is 1' under
water).

In spite of all the hassle this has caused, it is fortuitous. While
working on the water pump, i saw a big nut under the prop shaft, then
a big bolt, couldnt figger out where they came from. The another,
HUH? I looked all over for their source. Finally noticed he prop
shaft and transmission were slightly misaligned. AHA, HOLY Shi%. My
prop shaft is held by only one bolt to the transmission output and
even that is coming out. This coulda been a truly nasty surprise when
waaaaay out in the Gulf.

The Locktite company makes several things used to glue nuts to bolts,
so that the nut doesn't loosen. Which one you want, I am not sure. I
don't sell the stuff, but those who do would know. Your basic auto
parts house would have the stuff. This kind of thing may damage the
bolts, but it should be obvious if it has.

Casady

On Oct 6, 10:57*am, (Richard Casady)
wrote:
On Sun, 5 Oct 2008 19:16:09 -0700 (PDT),
wrote:



On Oct 5, 9:46 pm, Wayne.B wrote:
On Sun, 5 Oct 2008 17:17:37 -0700 (PDT),
wrote:

It seems to me that this thing should pump even if it does lose prime
because you would expect it to lose prime as the boat heels and waves
pass under. *Any thoughts?

Possible causes, more or less in order of likleyhood:

1. *Raw water impeller is tired and needs to be replaced.

2. *Raw water intake through hull fitting is fouled. * I once sucked
in a jelly fish. *Barnacle growth is common.

New impeller. *Recent bottom paint and defouling. *Besides, I can blow
down through the raw water seacock (with effort, it is 1' under
water).

In spite of all the hassle this has caused, it is fortuitous. *While
working on the water pump, i saw a big nut under the prop shaft, then
a big bolt, couldnt figger out where they came from. *The another,
HUH? *I looked all over for their source. *Finally noticed he prop
shaft and transmission were slightly misaligned. *AHA, HOLY Shi%. *My
prop shaft is held by only one bolt to the transmission output and
even that is coming out. This coulda been a truly nasty surprise when
waaaaay out in the Gulf.

The Locktite company makes several things used to glue nuts to bolts,
so that the nut doesn't loosen. Which one you want, I am not sure. I
don't sell the stuff, but those who do would know. Your basic auto
parts house would have the stuff. This kind of thing may damage the
bolts, but it should be obvious if it has.

Casady

If using "Lok-tite" tor "Thread-Loker" then use the blue stuff. it
will hold fasteners firmly but you can still wrench on them. Avoid the
red, because once it's cured and aged, it bonds so tight that
wrenching ( or screwdrivering) will bust heads on small bolts and
screws, or strip threads.

Red can be used if eventually you can get a torch to the casting and
heat it a bit , then the Loktite will melt or soften then you can go
to work usually without damage to parts.