Puncture Hole in Head Block, Rusty Cylinder

[mercruiser1969]

I have a 1969 Mercruiser 120hp 2.5L i4. Thought I blew the head gasket due to milky oil and water shooting out of spark plug holes. She'd turn over but wouldn't fire. When I took off the head, I found a puncture in the head next to the valves (see photo). Cylinder 1 is rusty but no visible cracks (see photo).

Any idea how I punctured the head? I was overheating until I replaced manifold, riser, circ pump and water pump. This happened after I fixed the overheating issue. Also curious if I'll have to replace the entire block due to the cylinder rust?

 

[Bt Doctur]

I think after 51 years it just rusted out

 

[Rick Stephens]

Salt water boat?

Doesn't really matter, water jacket rusted through.

 

[Scott Danforth]

51 years for a boat is a great run.

I would find a 3.0 and Alpha 1 Gen 2 to replace what you have.

 

[GA_Boater]

With the head rusted through, I would think the block is thin in places, too. Investing money in a new head and boring the block to clean up the bore along with parts could be money down the drain.

Is the boat used in salt water? Not that it matters as Rick said, but just something nice to know. Scott has the right idea - Find a donor boat, freshwater if you can. Or upgrade to a newer boat.

Welcome to the forums.

 

[Bondo]

Also curious if I'll have to replace the entire block due to the cylinder rust?

Ayuh,..... Welcome Aboard,....... You'll probably be far ahead to find a rotten donor boat, with a runnin' 2.5l or 3.0l to replace yer ole motor,......

You can find a whole runnin', rotten boat cheaper than a runnin' motor on a pallet,....

 

[mercruiser1969]

It was a salt water boat. Now freshwater. I am replacing the head block and cleaning the rust from cylinder with the hopes that it passes a compression test. If that fails, I’ll hone the cylinder.

Appreciate all the input.