Frost Plugs

[Watson27]

Hello everyone. Thanks for taking the time to read this call for help. Boat hasn’t been out this season yet. Was doing a tune up on my 2001 4.3 mercruiser EFI. When I got to the right side (non starter side) I noticed the two larger frost plugs were out. My heart sank. I did winterize my boat. I thought I took out all the blue twist in plugs and I even dump antifreeze down the water pump hoses. But I must have forgot one. My question is, what are the chances my block is not cracked? Oil level is fine. Do these plugs ever pop out and no damage has been done?

 

[itsathepete]

Core plugs are not designed to prevent damage to an engine from freezing but can pop out due to freezing or other conditions, like high pressure in the water jacket, or expansion of the block due to overheating. You can get a replacement plug or set of them from an auto parts store, just get the brass ones. It's worth reinstalling them and testing. If the block is cracked, the engine is done anyway. You're not going to hurt it anymore, unless you want to save the internals to use on another engine, still not likely to hurt them if you shut it down quickly upon noticing water in oil. good luck

 

[Watson27]

Core plugs are not designed to prevent damage to an engine from freezing but can pop out due to freezing or other conditions, like high pressure in the water jacket, or expansion of the block due to overheating. You can get a replacement plug or set of them from an auto parts store, just get the brass ones. It's worth reinstalling them and testing. If the block is cracked, the engine is done anyway. You're not going to hurt it anymore, unless you want to save the internals to use on another engine, still not likely to hurt them if you shut it down quickly upon noticing water in oil. good luck

Thank you for the optimistic and prompt reply. I was having a terrible week at work this was the icing on the cake.

 

[Bondo]

My question is, what are the chances my block is not cracked? Oil level is fine. Do these plugs ever pop out and no damage has been done?

Ayuh,.... Welcome Aboard,..... It depends on how cold it got, how quickly, 'n for how long it stayed that way,...

Put the core plugs back in, 'n light 'er up,....
It shouldn't take long to find out,...

 

[Watson27]

Ayuh,.... Welcome Aboard,..... It depends on how cold it got, how quickly, 'n for how long it stayed that way,...

Put the core plugs back in, 'n light 'er up,....
It shouldn't take long to find out,...

Good points. I really need a win here. Thank you for your information. I’ll repost when I get them back in. The one plug is between the the engine and mount. Not sure how easy that will be to pop back in.

 

[itsathepete]

Good points. I really need a win here. Thank you for your information. I’ll repost when I get them back in. The one plug is between the the engine and mount. Not sure how easy that will be to pop back in.

remove the exhaust manifold. use a socket exactly the same size as outer rim of the plug or use a flat piece of steel or brass the completely covers the plug and whack on it with a hammer. a piece of hard wood might even work

 

[nola mike]

Good points. I really need a win here. Thank you for your information. I’ll repost when I get them back in. The one plug is between the the engine and mount. Not sure how easy that will be to pop back in.

You can get a rubber plug for testing purposes

 

[Watson27]

remove the exhaust manifold. use a socket exactly the same size as outer rim of the plug or use a flat piece of steel or brass the completely covers the plug and whack on it with a hammer. a piece of hard wood might even work

I have a heat inductor at work. Do these studs usually break on boat exhaust manifolds?

 

[itsathepete]

Can't say I've had any break but it's possible. They should be stainless so hopefully not stuck with rust

 

[achris]

Can't say I've had any break but it's possible. They should be stainless so hopefully not stuck with rust

Ummm, no. They are steel, usually grade 8.8.

Chris.......

 

[itsathepete]

Ummm, no. They are steel, usually grade 8.8.

Chris.......

Perhaps I've been mistaken about the stainless but none of the exhaust studs I've seen from marine engines dating from 1969 to 1980s to today have been rusted so I assumed they were stainless. Grade 8 possibly (grade 8.8 denotes metric and is equivalent to grade 5 sae)