Marine Engine Block Freezing

[swall]

A friend of mine had a marine engine, 351 Ford Windsor, freeze up due to not being winterized. Only one freeze plug popped out, so the concern is that the block is cracked. Where would cracking be most likely to occur so that the suspect area can be mag particle inspected?

 

[MikeHalloran]

It's cheaper to replace that block than inspect it.



Mike Halloran
Pembroke Pines, FL, USA

 

[Fabrico]

Why can't you just put a new plug in it and pressure check it as is?

 

[grnegg]

The ford smallblock is quite prone to cracking between cylinders. This is where mine broke when frozen, even though the cooling system had been drained (obviously not well enough).

Good luck,
Grnegg

 

[MikeHalloran]

Fords have block drain plugs, but they're always corroded too badly to remove.

Mike Halloran
Pembroke Pines, FL, USA

 

[jbthiel]

I agree with Fabrico - but the only caviat is that if something is cracked/leaking and they use the engine they could ruin a lot of good parts. If it is an ocean going vessle it is probably just good insurance to tear it appart for a proper inspection. And than if it is bad they can reuse most everything. Of course this always leads to the "I might as well" syndrome.

As for weak spots - I would think it depends quite a lot on the age of the engine. I am not a Ford expert but almost all US V8's went on a diet in the mid 70's. If it is an old block it may be OK.

 

[MikeHalloran]

Smallblock 351s have always been thinwall castings.



Mike Halloran
Pembroke Pines, FL, USA

 

[SMOKEY44211]

Just to put to rest a misconception that the plugs found in the side of an engine block are "freeze plugs". The core plugs, to use the proper terminology, are there to seal the coolant cavity that is formed from the core that is supported by the mold when the block is cast. When water becomes solid the crystal structure that is formed takes up slightly more volume then when it was liquid thus providing the force that causes the casting to crack. I am willing to wager that the block in question is cracked. I have never seen an engine block that froze up to the point that the "core plugs" fell out that wasn't cracked.-----Phil

 

[boatmotorgod]

I agree with Fabrico, put a new plug in it and pressure test it. In my buisness I have seen quite a few Ford blocks push out the plugs without cracking the block. Though I can't recall a Chevy that survived without cracking. A core plug and pressure testing is far cheaper than a tear down for inspection.

 

[macquari]

I'm glad we don't have this problem downunder but we do have cracked blocks which can be hard to detect and as others have said previously a pressure test is the best way to go, mag particle will only show obvious cracks and there may be hidden internal cracks eg in oil galleries etc. with a good hot pressure test the engine will expand to normal running dimensions which will open up cracks which may seal when cold,also if a pressure test doesn't show any results I would then run the engine for a while and check for emulsion in the oil and coolant.
Good luck I hope the solution is the low cost one.

 

[frankiee]

I agree with "Smokey44211"
When younger I worked in scrap yard for 7 years and seen a lot of cracked blocks. They can crack anywhere and the "core plugs" do next to nothing.
The core plugs are put there in strategic points for removal of the casting material and they are not put in areas that would protect the device from freezing.
The power of ice is phenomenal and the elasticity of cast is not so good.
Sorry to say that if it were my boat I would replace it for my peice of mind. I mean, how could ice expand in such a way that it pops out a core plug and not weaken the cast block.
A lot of course depends on how your friends boat is used.
River use?? (Need a dependable engine)
Fishing use in small lake with a small second engine (dependability not that much of a factor)
Does the boat have just the one engine or two?
Just my opinion