I'm winterizing my 5.7 Mercruiser which has freshwater cooling. The most
important part of this rather simple process seems to be removing two
drains on the manifold elbow things on each side of the engine and one
on the heat exchanger. The latter one has a pencil zinc, the other two
do not.

Would it be prudent to install pencil zinc anodes on those two also? The
other one corrodes pretty quickly in salt water and I'm taking this rig
to the Bahamas, where I don't want all that warm salt water to corrode
my cooling system. What could it hurt?

Capt. Jeff

It is possible to "overzinc".

Are these OEM parts or aftermarket?

Odds are if they are OEM the engine builder put a zinc where it was felt one
was needed.

Sez Capt. Jeff
"...
removing two
drains on the manifold elbow things on each side of the engine and one
on the heat exchanger. The latter one has a pencil zinc, the other two do not.
Would it be prudent to install pencil zinc anodes on those two also? The other
one corrodes pretty quickly in salt water and...."

Capt, it depends on if your manifolds are fresh water cooled as well. Fresh
water cooling comes in several levels. (with mine the engine, manifolds and
risers are fresh water cooled, the elbows are not).
Putting zincs into the FWC portion of your system would not be a help.
With the engine running and warmed up, put your hand CAREFULLY on (maybe just
close would be best) the various cooling system components, The ones that are
HOT are part of the FWC system. The ones that are just barely warm or cool are
in the raw water circuit and should probably have some zinc protection.
Best wishes
Mike

You can not over zinc. But try one of the ones you have to make sure it
will fit.

"Messing In Boats" wrote in message
...
I'm winterizing my 5.7 Mercruiser which has freshwater cooling. The most
important part of this rather simple process seems to be removing two
drains on the manifold elbow things on each side of the engine and one
on the heat exchanger. The latter one has a pencil zinc, the other two
do not.

Would it be prudent to install pencil zinc anodes on those two also? The
other one corrodes pretty quickly in salt water and I'm taking this rig
to the Bahamas, where I don't want all that warm salt water to corrode
my cooling system. What could it hurt?

Capt. Jeff

You can not over zinc.

Be careful about such a broad statement.

I'll have to look up the reference again, but I've seen convincing arguments
made that
*extreme* amounts of zinc defeat the purpose.

Also notice where the 2" end of the zinc will end up WHEN it breaks off
in 2-4 months. Pencil zincs have a habit of eroding nearest the nut and
then breaking off (Especially in high flow environments). I have had
decent luck coating the first 1/2" of zinc nearest the nut with paint or
caulk and letting it dry before install.

Lawrence James wrote:
You can not over zinc. But try one of the ones you have to make sure it
will fit.

"Messing In Boats" wrote in message
...

I'm winterizing my 5.7 Mercruiser which has freshwater cooling. The most
important part of this rather simple process seems to be removing two
drains on the manifold elbow things on each side of the engine and one
on the heat exchanger. The latter one has a pencil zinc, the other two
do not.

Would it be prudent to install pencil zinc anodes on those two also? The
other one corrodes pretty quickly in salt water and I'm taking this rig
to the Bahamas, where I don't want all that warm salt water to corrode
my cooling system. What could it hurt?

Capt. Jeff