1977 century with OMC freeze out plugs

[Ajstangl]

My 1977 century freeze out plug behind the starboard engine mount is leaking. Engine 990230G. I used it about 11 years ago in salt water and after that trip two of the freeze out plugs were leaking and replace by a mechanic I don't know which ones he replaced. Any advice on the best way to get at this? And should they all be replaced. Also the bellow was never replaced on the boat. Should I do this as a preventative it is 49 years old. And any advice on this job?

 

[southkogs]

I've never changed the freeze plugs on that engine.

But, you shouldn't have bellows on that drive system. That's a Stringer, so you likely have a boot there on the transom. If it hasn't been changed in 50 years, then yes - I'd change it.

 

[Scott Danforth]

if the core plugs rotted out, then the motor was replaced at one time with a non-marine motor

the ones from GM when the motor was new were brass

first, determine if the block is rusted, the core plugs pushed out, or was the block swapped to an automotive one?

to R&R a core plug, usually the motor will need to come out of the boat to do it correctly. at that point, I would get one of the rubber expanding ones.

 

[Ajstangl]

I've never changed the freeze plugs on that engine.

But, you shouldn't have bellows on that drive system. That's a Stringer, so you likely have a boot there on the transom. If it hasn't been changed in 50 years, then yes - I'd change it.

OK thank you. I think I used the wrong name. The boot is that called a transome seal?

 

[Ajstangl]

if the core plugs rotted out, then the motor was replaced at one time with a non-marine motor

the ones from GM when the motor was new were brass

first, determine if the block is rusted, the core plugs pushed out, or was the block swapped to an automotive one?

to R&R a core plug, usually the motor will need to come out of the boat to do it correctly. at that point, I would get one of the rubber expanding ones.

Thanks. I know it is the original engine my father bought the boat new. Maybe I popped it out with too much hose pressure. But I had it in salt water once for a week and after this, a guy had to replace two other freeze out plugs. I can see the plug has paint over this one, so this was not one that was replaced but it looks like corrosion to me on the inside. Maybe the corrosion is from the block just seeping through. I had the water pump off and it was pretty corroded inside. While I am working on this is there a way to make sure there are no blockages in the circulation to the cooling system?

 

[Scott Danforth]

Maybe I popped it out with too much hose pressure

the core plugs will hold 50 psi without issue. you can not generate enough pressure for that to ever happen if the block is in good shape

But I had it in salt water once for a week ......but it looks like corrosion to me on the inside.

corrosion is the most likely culprit. that is your block eating itself from the inside on a raw-water cooled motor. did you flush the motor after salt-water use, or did it sit for a long time before the next use?

your boat is 50 years old, the motor is 50-55 years old (depending on the manufacturing date). they were designed to last 15 years

While I am working on this is there a way to make sure there are no blockages in the circulation to the cooling system?

you can pull the manifolds and elbows, inspect them for rust build up, and replace as required. short of pulling the head(s) and mechanically knocking out the rust buildup, not a lot to do. once corrosion gets to a certain point, you are looking at repower. at that point, I would rebuild the transom and look to go to something other than OMC

 

[southkogs]

The boot is that called a transome seal?

Correct.