"Rick & Linda Bernard" wrote in
:

I guess I missed something but what is the difference if you leave the
sea cock to the engine open or have this line to the packing. I
always expect to leak some water by the pump but expect the vented
loop to break the siphon. It is mounted high above the water line to
prevent the flooding the engine. Now if the vented loop is below the
water line or if it is plugged then all bets are off.

If the impeller seals well, it blocks water from going past it until it
turns when the engine comes on. I don't think I've ever seen a regularly-
maintained (replaced) impeller allow enough water past itself to make any
difference, certainly not filling up the exhaust system. But closing the
seacock is always a good idea, if only a pain in the ass. There's no
"vented loop" between the seawater intake to the cooling system and the
water pump. If there were, the pump would never prime as the impeller
pumps aren't self-priming without seawater pressure trying to push through
them. That's why outboard motor impellers are located in the foot
underwater.


One thing to think about is if the shaft was turning without the motor
running the seal could actually be a small pump and be pumping water
back into the engine via the tube. It would not be a very efficient
pump but might develop enough head to overcome the level difference on
the vented loop especially if you are healed over. If that happens it
will flood the engine.

Good point.


When I ran a PSS seal on a sailboat I wondered about that so I got the
ventless/tubeless one. One disadvantage to the tubeless one is that
you need to burp the seal to get the air out. Kind-a ends thoughts of
a dry bilge. Burping would be a real pain on my current boat.
Currently I am real happy with the new TFE packing material using a
standard stuffing box.

I suspect the reason we got the tubed model is because you'd have to be a
circus contortionist weighing 80 pounds to hang upside down to get back to
where this rubber boot is to burp it. Amel Sharki's engine room is DEEP!
And there are many places a fat WASP just doesn't fit...(c;


Perhaps someone who has a PSS seal could disconnect the tube at the
pump and hold it at water level. Block the end at the raw water pump
and run the engine in gear at a shaft speed similar to running at hull
speed without engine and out of gear. See if you get any pumping
action. If so raise the tube end higher and measure the elevation at
which the surging stops. If you get a couple of inches you are
probably ok. If you get more then that I would suggest not sailing
out of gear without the engine running. Put it in reverse and
consider using the tube as a vent to allow the air to escape.


I solved the problem and kept the injection. It simply has an inline water
valve to open when she comes out of yard on her sea trial, which can be
shut off and forgotten like the tubeless one after that.

Larry

"Larry W4CSC" wrote in message
...
"Rick & Linda Bernard" wrote in
:

I guess I missed something but what is the difference if you leave the
sea cock to the engine open or have this line to the packing. I
always expect to leak some water by the pump but expect the vented
loop to break the siphon. It is mounted high above the water line to
prevent the flooding the engine. Now if the vented loop is below the
water line or if it is plugged then all bets are off.

If the impeller seals well, it blocks water from going past it until it
turns when the engine comes on. I don't think I've ever seen a regularly-
maintained (replaced) impeller allow enough water past itself to make any
difference, certainly not filling up the exhaust system. But closing the
seacock is always a good idea, if only a pain in the ass. There's no
"vented loop" between the seawater intake to the cooling system and the
water pump.

Yes - the vented loop is normally after the heat exchanger and just prior to
the exhaust elbow. Correct - a vented loop before the pump would cause
problems.

If there were, the pump would never prime as the impeller
pumps aren't self-priming without seawater pressure trying to push through
them. That's why outboard motor impellers are located in the foot
underwater.


One thing to think about is if the shaft was turning without the motor
running the seal could actually be a small pump and be pumping water
back into the engine via the tube. It would not be a very efficient
pump but might develop enough head to overcome the level difference on
the vented loop especially if you are healed over. If that happens it
will flood the engine.

Good point.


When I ran a PSS seal on a sailboat I wondered about that so I got the
ventless/tubeless one. One disadvantage to the tubeless one is that
you need to burp the seal to get the air out. Kind-a ends thoughts of
a dry bilge. Burping would be a real pain on my current boat.
Currently I am real happy with the new TFE packing material using a
standard stuffing box.

I suspect the reason we got the tubed model is because you'd have to be a
circus contortionist weighing 80 pounds to hang upside down to get back to
where this rubber boot is to burp it. Amel Sharki's engine room is DEEP!
And there are many places a fat WASP just doesn't fit...(c;


Perhaps someone who has a PSS seal could disconnect the tube at the
pump and hold it at water level. Block the end at the raw water pump
and run the engine in gear at a shaft speed similar to running at hull
speed without engine and out of gear. See if you get any pumping
action. If so raise the tube end higher and measure the elevation at
which the surging stops. If you get a couple of inches you are
probably ok. If you get more then that I would suggest not sailing
out of gear without the engine running. Put it in reverse and
consider using the tube as a vent to allow the air to escape.


I solved the problem and kept the injection. It simply has an inline
water
valve to open when she comes out of yard on her sea trial, which can be
shut off and forgotten like the tubeless one after that.


There are other issues that may cause an air bubble. A diver cleaning the
prop. A broach on a windy day. and there are probably a few others that I
can't think of.

I was always carefull to always burp my PSS but I did hear of someone that
ran one with a air bubble. I made such a racket that they shut down the
engine to figure out what was wrong. Burped the unit and everything ran
fine after that.



Larry

... A broach on a windy day.

As apposed to a broach on a calm day

Doug
s/v Callista

"Doug Dotson" wrote in
:

... A broach on a windy day.

As apposed to a broach on a calm day

Doug
s/v Callista

Broaching on a calm day takes a highly skilled captain.....(c;