I know you know better than that.

I have had motors run with with a bent pushrod on one side not allowing the cylinder to evacuare and did not experience any damage to the other valves pushrod.

Still sounds like A. water on a startup that had bled down there and filled the cylinder and hydrolocked but more than likely it was a corrosion that temporarily stuck both valves.

How soon after starting was a miss or problem noticed? How long was the boat sitting before it was started and noticed?
Is it a saltwater boat? How old are the risers?

Check the rocker arm really well for any signs of pushrod contact outside of the cup. Maybe the lifter plunger collapsed and that eliminated all of the preload on it. That could leave enough room for the pushrod to come out of the rocker arm cup. I've seen them do that and push off center on the rocker or come out of the guide plate and bend the pushrod. The rocker arm will have some evidence of the pushrod hitting it somewhere other than the cup.
Eddie

I was asking him what his thinking is, Note the ? LOl.

Anyhow, without further evidence, bending pushrods and gutting a lifter in the same cylinder would have me looking for something more tramatic as you are saying.

I've never gutted a lifter - I have only seen this on lifters with wire retainers not running enough preload.

I have, however, bent pantloads (yes, that's a number...LOL) of pushrods. Typically due to over rev.....that used to be my trademark. Double LOL.

Eddy. The exhaust lifter bit the farm. The intake pushrod bent.

Oh crap. Never mind then. Disregard everything that I said. Guess I should have read more carefully.lol

Eddy: That's why I pointed it out. Would be very easy to miss that and thus not give the OP valid info. I could see many others missing it to.

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Just dug my grey matter and do remember a cust's motor that gutted an exhaust lifter. Was a 502. Freakin thing sounded like a bunch of firecrackers. Intake psuhrod/rocker/etc/etc was fine. Exhaust pushrod wasn't, but it was lying in the head. It may have had a broken exhaust valve spring too...that part I don't really remember.

The guy limped it back approx 10 miles.

Is the intake lifter in good shape? I assume it didn't collapse?

The motor had only sat for 1 day prior to this event. Also .this happened after running for about 45 minutes...no water in cylinder. It is a saltwater boat. The exhaust is nee this year. All clean and dry inside. im still baffled...i will try to do more inspection...didnt want to pull the head.

Just as suspected. Engine shop says one caused the other. Collapsed lifter not allowing gases to escape
..caused pushrod failure on intake....said it's prettu common

So you are saying exhaust lifter collapsed and because exhaust wasn't fully opening ,intake pushrod bent ...I gotta cry BS