Engine sputters and dies after running great all day

[Greentree 0]

So looking for some advice on a problem I’m just recently having, 

My boat is a 1991 falcon with a 351 Windsor, I recently just purchased this boat when I purchased it the block was cracked so I bought a rebuilt block and swapped motors I had it running great then just last weekend I was cruising along about 3/4 throttle and it slowly puttered out like it wasn’t getting fuel then it died, it then started up again with no issues.. so I headed back closer to the boat launch and tried to get the same issue to happen .. it’s did again at about 3/4 throttle just slowly sputtered and eventually died but wouldn’t start again. I figured it was a carb issue so I rebuilt the carb and now it still won’t start but it’s getting fuel what could be my issue? Any advice would be greatly appreciated 

[InfinitySurf 302]

Dirty fuel filters restricting flow? Also possible the Low pressure fuel pump is going out and cant feed enough fuel after running higher throttle for a while.