Chipped BF75L block

I recently bought a Honda BF75 Long shaft outboard that has a rather large "chip off the ol' block", and would like some sage advise on how much of an issue this is. The missing bit of block came off with a screwdriver as a single chunk and had salt crust around it. I should have grabbed a photo with the chip in tact, but I've attached several photos of where it used to be.

The outboard runs well, and I will be performing a compression test on it soon. The prior owner didn't use it much, so I'm not sure what history the motor has (other than being used in salt water). Does the outboard need the entire cylinder housing replaced, or can I patch this with a good epoxy?

Also, can anyone explain what might have caused such a large chunk of block to come off so easily? What really scares me is the exposed bolt thread.

I spoke with a marine mechanic who said it was possible the salt got into the block and over time, the salt corrosion produced the chip through expansion and contraction.

When I hear of a "cracked block", I think of a crack that runs into the combustion chamber. This is more of a "chip" that seems to be isolated to just the exterior.

Compression test results are looking good - 120psi on both cylinders (<5psi difference on the gauge)

No-one has seen this kind of issue before I take it? Am I mistaken in thinking this is more of a "cosmetic" issue? Having the bolt threads exposed is definitely concerning, but the motor seems like it will still hold together. It seems like the only issue I might have is if I ever need to change the head gasket.

I wrote a response to your post several days ago but it didn't publish for some reason. I can't make out from your photos what that exposed bolt is clamping. Is it the cylinder head? If so, yes, you could have problems there if you were to disturb it. But for now, it looks as if there is enough thread engagement left....along with a bit of "corrosion bonding"....to keep it in place.

If it is a head bolt, i doubt applying epoxy there would gain you much strength. And, the cleaning you would need to do in order to get the glue to adhere might cause the aforementioned corrosion bond to be broken and leave you worse off than you are now.

It has good compression and it runs? I'm inclined to call it a DNFW as my old pappy used to say. Or, in other words, I'd leave it alone but keep an eye on it.

Good luck