Freeze-out plug leak
 

Hello, I am a new owner of a 1969 Cal 29 with an Atomic 4. This is a fresh water boat on Lake Michigan. After winter storage, I fired up the engine and noticed a large amount of water coming out the top of it. Turns out there is a non-threaded hole on the top of the engine, starboard side towards the back. Looks like the hole was braised shut with a small bronze disc about the size of a silver dollar and it came off when I started the engine (thank goodness I found it).

Does anyone know how I go about fixing this? Seems really odd that this somewhat crucial port would be sealed up in such a simple manor. Am I missing something?

UPDATE: I found a photo that shows this part and am attaching it.

UPDATE 2: changed the title of post so it’s easier to find when searching for this issue

Welcome Lokeypod,

That is a frost plug that has popped out - see this thread for info - https://www.moyermarineforum.com/for...rost+plug+head

And of course you might now be concerned that the engine was not properly winterized and other damage exists. The thread linked above has a suggestion from Ken at Moyer (our hosts) for a temporary fix with an expandable rubber plug. That might be the way to go and then do a pressure test to see if the rest of the cooling system is ok.

Let us hope that this frost plug was the only problem - how does the engine oil look? Nice and clear or milky?

Best,

Peter

Thank you! I'll check the oil next time I'm down there to see how the oil fared the winter

Actual name for that is a 'core plug'. When the head is cast, the internal water passages are made by a piece called a core. After the head cools, the core has to be removed from the inside of the head, hence this (and other) passage. Once the core is out, the passage gets machined and a plug installed - the core plug. You'll also find a couple in the exhaust manifold.

More detail
 

The Atomic 4 uses two different types of core plugs. Be sure to get the right one for the application:
https://www.moyermarineforum.com/for...58&postcount=4

I still have the plug, so I guess I can just pop it back in and see what happens. I'll buy a couple back ups too. Thanks for all of your help!

Hello lokeypod.

You may have already seen this, but just in case, here is Don Moyer's answer to a FAQ about installing core plugs:

FAQ’s: Cooling
Freeze-out plugs were originally installed over a small ridge cast into the lower part of the hole in the block, head or manifold. Here are your options for repair, starting with the least invasive and leading to the more complicated procedures:

1) If the plug has some dome shape remaining, you could take a flat punch (like maybe a 1/2″ bolt) and flatten the plug. These plugs are designed to seal around their OD by flattening out their dome shape. Flatten the plug by pounding in a circular pattern around the center, but not directly in the center. The challenge is to flatten the plug without causing a concave dimple in the center, which would reduce the ultimate outward expansion of the plug.

2) If the plug is already flat, you may be able to seal it using epoxy of the type West Marine sells in small repair kits. Before using epoxy, be sure to clean the surface of the head and plug extremely well.

3) You can replace the plug with a new one from our online catalog (Product
number: OBLK_14_125) and reseal around its circumference during installation. Old plugs can be removed by drilling a small hole in their center and then inserting a punch and prying the cup out by pounding on the side of the punch. Since the inner circumference of the hole will probably be less than perfect, we recommend the use of JB Weld to seal the new plug. Flatten the new plug as in the first option above.

4) If, after removing the old plug, you discover that the ridge in the casting is deteriorated to the point that it will not support the pounding it will take to seat a new dome shaped plug, you can ream the hole to a slightly larger size and install a “cup” type plug. In our own rebuilding work, we routinely ream holes for the larger plugs (used in the block and head) to 1-1/4″, and to 15/16″ for the smaller plugs (two used in the manifold and one in the head).

5) For on-boat repairs, where poor access prevents repairs involving reaming etc., there are rubber expansion plugs available from many automotive parts stores which may work to seal a hole (at least on a temporary basis) that is too deteriorated to accept a dome type plug without the need to ream the hole. – Updated: December 22, 2003

Hi lokey,

Back in the day, we used to smear a bit of Ford brand weatherstrip glue all over the back side(water side) of those plugs to help with any sealing problems and to give a little more corrosion protection. I think any goop that seals would be helpful. not required if you can get it to seal though.

Russ

Update: solved!
 

Thought I’d update this post for future folks that might run into this.
I bought a couple new freeze-out plugs from Moyer and popped one in. I used a ball peen hammer to expand/concave the plug in the hole and it sealed up well.

Thanks for everyone’s suggestions and help!