"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!

In article ,
"Jeffrey P. Vasquez"
wrote:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

One thing to check isif the shaft that drives the impeller is in one
piece. I had a JABSCO where the shaft was made in two parts that were
pressfit together. Water leaked thru a failed seal and corroded the
shaft connection to the point that the pressfit connection failed.
Pully turned, but impeller didn't. I found it by turning over the
engine with the pump faceplate off and watching the impeller itself.

Bruce in alaska
--
add a 2 before @

In article ,
"Jeffrey P. Vasquez"
wrote:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

One thing to check isif the shaft that drives the impeller is in one
piece. I had a JABSCO where the shaft was made in two parts that were
pressfit together. Water leaked thru a failed seal and corroded the
shaft connection to the point that the pressfit connection failed.
Pully turned, but impeller didn't. I found it by turning over the
engine with the pump faceplate off and watching the impeller itself.

Bruce in alaska
--
add a 2 before @

Older Yanmar pumps have trouble keeping the pressure up to maintain
the flow unless the pump clearances are correct. This is more of a
problem on boats with hot water heaters, engine driven refrigeration
and water-lift exhausts.

When replacing the raw water pump impeller it is important to check
the clearance between the parting surface and the impeller. Make sure
the impeller is all the way in the pump then with a straight edge and
a feeler gauge check the free clearance of .001 to .002 of an inch. If
there are too gaskets on the pump plate instead of the thin one
supplied by Yanmar, pumping pressure will be effected.

On 2GM and 3GM engines that are salt water cooled a stuck closed or
missing thermostat will bypass the water all the time causing the
engine to overheat.

From the author of four books on boat refrigeration.
http://www.kollmann-marine.com

Older Yanmar pumps have trouble keeping the pressure up to maintain
the flow unless the pump clearances are correct. This is more of a
problem on boats with hot water heaters, engine driven refrigeration
and water-lift exhausts.

When replacing the raw water pump impeller it is important to check
the clearance between the parting surface and the impeller. Make sure
the impeller is all the way in the pump then with a straight edge and
a feeler gauge check the free clearance of .001 to .002 of an inch. If
there are too gaskets on the pump plate instead of the thin one
supplied by Yanmar, pumping pressure will be effected.

On 2GM and 3GM engines that are salt water cooled a stuck closed or
missing thermostat will bypass the water all the time causing the
engine to overheat.

From the author of four books on boat refrigeration.
http://www.kollmann-marine.com

On Sun, 04 Jan 2004 19:29:28 GMT, "Jeffrey P. Vasquez"
wrote:


"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!


I had one impeller fail by the rubber coming adrift from the metal
bushing - everything looked fine, but the rubber didn't turn.




--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

On Sun, 04 Jan 2004 19:29:28 GMT, "Jeffrey P. Vasquez"
wrote:


"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!


I had one impeller fail by the rubber coming adrift from the metal
bushing - everything looked fine, but the rubber didn't turn.




--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

On Sun, 04 Jan 2004 19:13:50 GMT, "Jeffrey P. Vasquez"
wrote:



Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.




Rodney Myrvaagnes J36 Gjo/a


Does one child rape really change Strom Thurmond's lifetime record?
For better or worse?

On Sun, 04 Jan 2004 19:13:50 GMT, "Jeffrey P. Vasquez"
wrote:



Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.




Rodney Myrvaagnes J36 Gjo/a


Does one child rape really change Strom Thurmond's lifetime record?
For better or worse?

Rodney wrote:
I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.

Yes, it's raw. I always leave the door open to be enlightened when I know I
am not an expert.