Heat Exchanger Zinc Change out

[britinusa]

Reading lots of info about changing the Heat Exchanger Zinc, but unable to find anything that indicates if much water is going to come out of the heat exchanger and if there is any need to bleed the system after?

I can see where the zinc is located. It's on the underside of the Heat Exchanger.

I understand that it's raw sea water that will come out, but how much? I presume the Raw Water shut off should be closed when removing the zinc.

Paul

[mark_53]

Not too much water will come out.  Use a flexible one quart container.  Maybe a cut down plastic milk jug.

[britinusa]

Cool, thanks.

And do we have to bleed the HE after zinc replacement??? (is it possible to bleed the HE?)

Paul

[Steve McGill]

Paul,

You do not have to bleed, the system is not closed, the intake in the thru hull on the engine side and the exhaust is where its expelled.

As previously stated the amount of water with ether the 2" or 3" HE is minimal.

A 3 minute job and you are good for another 6 months to a year.

Enjoy,

Steve

[Stu Jackson]

Answers are correct.  I don't bother to catch the minor amount of faw water, I let me shirt sleeve soak it up!   

No bleeding; only bleed is for the fresh water coolant system. 

I check mine every three months, 'cuz if you MISS it deteriorating, you're gonna have to remove the HX to get the broken stub out.     Not a fun job 'cuz you didn't do 43 seconds worth of a check.

[Kevin Henderson]

Paul,

Changing the Zink is a pretty straightforward process albeit a little difficult to get to.  The first few times I did it I crawled into the aft berth to get close to the action.  I now change the zink from in front of the engine since I know a litle more about what to expect.  Yes... be certain to close the thru hull!  As with any evolution the first time is always scary and it seemed to me that a lot of water came pouring out of the HX... this is normal so don't be afraid.  a good jug and some rags/sponges helps to keep the mess down.  Once the zink is out, stick a pencil into the hole to see how deep your new zink will go.  You do not want to accidentally install too long of a zink and puncture the interior causing a coolant leak... so be careful!  Also do not use any form of teflon tape to seal the threads... the zink has to have full metal to metal contact to work.  
No need to flush the HX... just fire up your engine and and watch for water coming out the exhaust.  Then make certain you have no leak at the HX and then have a cocktail congratulating yourself on a job well done!  

[Ron Hill]

Paul : Only about 1/2 to 1 pint of water comes out - not much that would overflow a large paper cup!

You don't need to shut off the raw water thru hull as the HX in on the exhaust side of the RW pump.

You are in salt water!!  So I'd do as Stu recommends and check the Zn every 3 months.  
You also failed to mention if your Zn is a 3/8" or 1/2" diameter? or the engine usage?  

I'd still check every 3 months until you find that the Zn isn't being "eaten up" and then you can extend the check to every 4 months!!

A thought

[KWKloeber]

Reading lots of info about changing the Heat Exchanger Zinc, but unable to find anything that indicates if much water is going to come out of the heat exchanger and if there is any need to bleed the system after?

I can see where the zinc is located. It's on the underside of the Heat Exchanger.

I understand that it's raw sea water that will come out, but how much? I presume the Raw Water shut off should be closed when removing the zinc.

Paul

Paul,

it might ne easier to disconnect the Hx feed hose at the sea water pump and drain the hose in to a container.  Then you will have drops out lf the Hx.

FWIW, the Hx *should* also be bonded to a good ground.  I don't rely on the M-25 or XP brackets because they don't make a great ground and/or sometimes there's (I do have) a rubber pad between the clamps/bracket/Hx to cut down on vibration and damage to the shell.   A 5/16" ring terminal on the end cap bolt, w/ a bonding (GREEN) wire to good ground on the engine works or to a ground buss.  I usually make them up w/ 10 or 12 awg only because I like hefty, but any gauge will do.

Ken

[Ron Hill]

Guys : Electoral erosion is going to be between the copper in the HX and the salt water.  That's why the important ground is between the Zn and the HX case!!  

Just make sure you have a clean surface on the brass ZN holder and the threads on the HX case. Don't coat the threads as you might isolate the anode - so it won't do its job. 

That's why I always recommended (in many posts / Mainsheet tech notes) to purchase a battery terminal cleaning tool from an auto supply (a couple of $).  
You can use the male brush to go inside the HX threads and make sure they are clean of corrosion and get a good contact (grounding) with the Zn holder when you screw it in!!

A few thoughts  

[KWKloeber]

To clarify re: why to bond the Hx -

Bonding the engine and components is required by ABYC Standard E-11. 
If the component-to-engine electrical connection is broken, a bonding wire is required.  This is for both galvanic corrosion (folks who might not be as diligent as they should at servicing zincs.) and for safety (to trap stray current.)  Because even the *expert websites* get confused by the term, just to be 100% precise for folks -- we're talking about galvanic corrosion (electron loss from one metal on another dissimilar metal on the galvanic scale) - versus electrolysis (e.g., our chargers producing hydrogen and oxygen gas from our wet cell batteries.)

K

[KWKloeber]

This is for both galvanic corrosion (folks who might not be as diligent as they should at servicing zincs.)

To be accurate, this includes all anodes.  Mates and Matettes, use MAGNESIUM anodes in fresh water, not ZINC anodes, which are for salt water!

kk

[britinusa]

A stitch in time!
As I had the aft berth cushions removed for the install of the NEMA 2000 network wiring beneath the helm, I raised the deck board and looked for the Zinc. Easily found, there's a big label adjacent to the Zinc.

No big deal to remove it, but OMG! Where is it!

Followed the advice and measured the max length for a new Zinc, Max of 3.25"

I was able to drill into the remaining part of the zinc and then remove it with a pair of pliers. The PO had left a spare zinc onboard, but I wasn't sure if I could get a longer one than what he left behind. Turns out the one he had left was a standard and I found them at WM. Brought two back to the boat.

Used a wire brush to clean the crud off the threads on the outside and inside of the Zinc Nut (holder) then inserted the new zinc and installed it in the heat exchanger.

You guys were right, I collected about 1" of water in the cut off milk jug I used to catch it.

Now.... how do I replace that 'water' that came out? Will it just refill when I start the engine?

Paul

[Stu Jackson]

Now.... how do I replace that 'water' than came out? Will it just refill when I start the engine?

Yes, it will refill, it is raw water, not coolant.  You don't have to refill anything.

[Ron Hill]

Paul : Don't worry about the water that came out of the HX as the raw water pump will fill it backup as soon as the engine starts!!   

[britinusa]

The saga continues.

First I have to say thanks to everyone that has contributed to this forum & the tech wiki.

I decided that if the zinc was beyond it's best by date, then I had better check the rest of the raw water system.

1st the Raw Water Filter in the Head. Definitely not blocked, but did have a lot of flotsam, so I removed it and cleaned it out. I need to get a spare filter (wire netting).

Then took the front off the Water pump. Arggggg! it had calcium build up (or some crud) and at least one of the vanes was permanently bent (ie, still bent when not touching the pump bottom (don't know the name of the bit that shapes the chamber near the bottom).

The inside face of the pump cover was, IMHO, horribly scarred. I had a spare pump on board, so I swapped them out. I'm hoping that it's possible for me to recondition the old pump.

After replacing the pump, I removed the new cover off the front and applied a little lube to the impeller to ease it's first run.
Then we started the engine and checked for water flow out of the exhaust. There's much more! It comes out in spurts and I would guess about a cup at a time.  No leaks at the HX zinc, nor at the newly installed pump.

Doing well so far.

So I took the next step and looked, yet again, at the temperature sender. I removed the sender and cleaned out the housing threads with a battery post cleaner (looks like a small wire bottle brush) and reinserted the sensor.
Started the engine but still nothing reading on the gauge. I shorted the gauge to the block and got full gauge reading.

Took out my New Laser Thermometer and checked the engine temp.... 99F !!!!! (the temp read within a few degrees as I checked around the engine)

Then, much to the admiral's dismay, I suggested that I shut off the raw water inlet and watch for engine temp rising.

It did! I chickened out at 115F(laser themo) at which time the gauge rose above the 120F mark. (gauge reads 120 - 160 - 180  - 200 - 240) It was probably reading about 130F-140F

Shortly after the needle on the gauge rose above 120, I opened the raw water shut off valve and let the engine run for another 5 minutes and the temp dropped down again (below the 120F mark on the gauge) to 99F on the laser thermo.

Can this be real? Can the engine really be running that cool????

Does it do the engine any harm???

And can I recondition the pump? I think I have to polish the inside cover (if I polish both sides it's reversable?) clean out the inside and replace the impeller, replace the O-ring between cover and pump body. There was no sign of weeping, so should I also replace the seals?

One last note. There's a cover just above the top left (stbd) pump cover screw, that cover came off when I was removing the old pump. Inside is a black threaded rod that is held in place by a thin nut and a long nut (3/4"long~) I had to remove those two nuts in order to put the new pump in place on the 4 mounting bolts. Not sure what that rod does, any ideas. The nuts cannot turn if the pump is in place, so I left the outer one loose until the pump was installed then tightened it up and put the cap back in place.

I'm starting to feel a little more comfortable working on the engine. It's starting to make sense.

Paul