Plugging exhaust to avoid hydrostatic lock
 

Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a disassembled
exhaust system to know what the plumbing geometry looks like inside. It's
not clear to me how this works, because you obviously have raw water going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up your
I/O exhaust ports *when the engine is running*? Or does the running engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored or
just drifting? I have the usual rubber flaps just inside the ports on the
stern, but I'm thinking of something like a foam stopper that you'd shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.

Plugging exhaust to avoid hydrostatic lock
 

Richard J Kinch wrote:
Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a disassembled
exhaust system to know what the plumbing geometry looks like inside. It's
not clear to me how this works, because you obviously have raw water going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up your
I/O exhaust ports *when the engine is running*? Or does the running engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored or
just drifting? I have the usual rubber flaps just inside the ports on the
stern, but I'm thinking of something like a foam stopper that you'd shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.



If you already have rubber flaps similar to those in this link, you
should be fine.


http://www.westmarine.com/webapp/wcs...llpartial/30/0

Putting styrofoam plugs on a lanyard might be a fairly questionable
solution.
If you forget to remove your plugs before starting and they "pop out"
what keeps the lanyards out of the props, most likely pretty nearby?

It's hard to imagine serious following seas hitting your stern when
"anchored out," assuming that you anchor from the bow like 99% of us do
and that your boat is free to circle the hook as the wind or current
changes.

Plugging exhaust to avoid hydrostatic lock
 

On Mon, 03 Apr 2006 01:20:02 -0500, Richard J Kinch
wrote:

Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a disassembled
exhaust system to know what the plumbing geometry looks like inside. It's
not clear to me how this works, because you obviously have raw water going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up your
I/O exhaust ports *when the engine is running*? Or does the running engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored or
just drifting? I have the usual rubber flaps just inside the ports on the
stern, but I'm thinking of something like a foam stopper that you'd shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.

Go here http://tinyurl.com/lullf and look at part # 7. That's what I have
in my exhaust to keep water from entering.
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************

Plugging exhaust to avoid hydrostatic lock
 

Plugging exhaust to avoid hydrostatic lock
 

Probable dumb question, but does a stern drive that is raw water cooled have
a similar baffle? The sea water enters through holes in the lower drive leg
and leaves through the prop hub. (I ordered a manual but haven't received it
yet.)

"JohnH" wrote in message
...
On Mon, 03 Apr 2006 01:20:02 -0500, Richard J Kinch
wrote:

Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk
and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a
disassembled
exhaust system to know what the plumbing geometry looks like inside. It's
not clear to me how this works, because you obviously have raw water going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up
your
I/O exhaust ports *when the engine is running*? Or does the running
engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored
or
just drifting? I have the usual rubber flaps just inside the ports on the
stern, but I'm thinking of something like a foam stopper that you'd shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.

Go here http://tinyurl.com/lullf and look at part # 7. That's what I
have
in my exhaust to keep water from entering.
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************

Plugging exhaust to avoid hydrostatic lock
 

On Tue, 4 Apr 2006 22:41:39 -0700, "William Andersen"
wrote:

Probable dumb question, but does a stern drive that is raw water cooled have
a similar baffle? The sea water enters through holes in the lower drive leg
and leaves through the prop hub. (I ordered a manual but haven't received it
yet.)

"JohnH" wrote in message
.. .
On Mon, 03 Apr 2006 01:20:02 -0500, Richard J Kinch
wrote:

Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk
and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a
disassembled
exhaust system to know what the plumbing geometry looks like inside. It's
not clear to me how this works, because you obviously have raw water going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up
your
I/O exhaust ports *when the engine is running*? Or does the running
engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored
or
just drifting? I have the usual rubber flaps just inside the ports on the
stern, but I'm thinking of something like a foam stopper that you'd shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.

Go here http://tinyurl.com/lullf and look at part # 7. That's what I
have
in my exhaust to keep water from entering.
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************


Yes. My sterndrive is raw water cooled. The baffles in the exhaust pipes
have nothing to do with the cooling. They just allow the one-way flow of
water (and exhaust).
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************

Plugging exhaust to avoid hydrostatic lock
 

Thanks. I know that the baffle's only purpose is to prevent water from
entering the exhaust. I just didn't know if there was a baffle in the
exhaust of a sterdrive because of the way the exhaust is routed, compared to
an inboard engine's exhaust system.
When I got water in my engine a couple of years ago, the woman at the parts
counter mentioned the baffle not working, but she said some other things,
too, that made me question how knowledgable she was and if she confused my
boat with someone else's, or if she misunderstood the mechanic.

"JohnH" wrote in message
...
On Tue, 4 Apr 2006 22:41:39 -0700, "William Andersen"
wrote:

Probable dumb question, but does a stern drive that is raw water cooled
have
a similar baffle? The sea water enters through holes in the lower drive
leg
and leaves through the prop hub. (I ordered a manual but haven't received
it
yet.)

"JohnH" wrote in message
. ..
On Mon, 03 Apr 2006 01:20:02 -0500, Richard J Kinch
wrote:

Having just gone through a breakdown where I had to rule out hydrostatic
lock (turned out to be a half-bad starter), I'm thinking about the risk
and
how to avoid it on my 5.7 Mercruiser I/O. I have never seen a
disassembled
exhaust system to know what the plumbing geometry looks like inside.
It's
not clear to me how this works, because you obviously have raw water
going
through the exhaust all the time in a running engine.

Can you get hydrostatic lock from a following sea or chop splashing up
your
I/O exhaust ports *when the engine is running*? Or does the running
engine
prevent that? How much of a wash does it take if your engine is cut? I
have 4-inch stainless ports, with a slightly uphill slope through the
rubber tubes to 6-inch risers. The bottom of the port is only about 8
inches above the waterline. Seems like a little too much trim astern
and
some wave action, and you'd have water quite a bit over those ports.

Do people use some kind of plugs or stopper on the exhaust when anchored
or
just drifting? I have the usual rubber flaps just inside the ports on
the
stern, but I'm thinking of something like a foam stopper that you'd
shove
into the exhaust port. If you forgot to remove it before starting, it
would just pop out, captured on a lanyard.

Go here http://tinyurl.com/lullf and look at part # 7. That's what I
have
in my exhaust to keep water from entering.
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************


Yes. My sterndrive is raw water cooled. The baffles in the exhaust pipes
have nothing to do with the cooling. They just allow the one-way flow of
water (and exhaust).
--
'Til next time,

John H

******************************************
***** Have a Spectacular Day! *****
******************************************