Ok I tore apart my engine and found out that it's a 454 not a 540 like I was told.
So I'm thinking about buying a short block or short block kit.
Which brings me to my next question which do you prefer for a boat engine block.World Merlin III or Dart big M.
I hear that the dart has an issue with pumping all the oil into the top end faster then it can drain back to the pan.
Does the world have the same issues.
any advice would be greatly appreciated.

I think the oil drain hole behind the timing chain can be opened up in the dart block.

Single engine? How did it go thinking it was a 540? Just curious

Well thought it was a 540 but after it wouldn't idle I pulled the timing cover and noticed it had way to big a cam.
That lead me to pulling the engine to change the cam and while out decided I would go thru the engine to check everything out.
I then found out it was a 454 instead of a 540.
so now I'm thinking about building a 540 and using my old heads after I put inconel valves in them etc.

How big was way too big of a cam?

to answer your question,they are both good blocks but for me it,s the big m every time.i have used both and i feel the dart is just better

Solid crane cam 262/272 @.050 .708 lift and 110 lobe seperation.

Have you ran them on boats.What's the trick to keeping it from pumping all the oil to the top.end at 5000-6000 for extended periods of time.

9.8 or 10.2 deck? Reason I ask is that the GMPP gen 6 502 block is machined and readily available from what I’ve read and seen posted by Mike T here. This could be another choice for you.

Well I currently have a Mark IV block if I buy a gen 5 or 6 block a lot of my accessorys won't fit( 13 quart oil pan.front cover etc)which would offset the difference in cost of the aftermarket block.
I would have at least 1000 dollars( probably more)in those type of items which then puts me about even with an aftermarket block.