Not true with a 454 block. 454's have water jackets between the cylinders which limits your bore to .060 or so. Some earlier 454 blocks I've seen up to .100 plus over but I'd never take it that far. Some will take a Siamese 502 to the max however not recommended by most. 4.500 is not real uncommon. Much over that is up to individual. Some will take up to 4.560/4.600. So in a nutshell not advised to go over 4.500 bore on 502. Anything over that your looking at aftermarket block. Dart, Merlin, etc.

Plus if you get over 4.250 stroke your looking for potential long or short term catastrophe. Again some have clearanced for a 4.500 stroke/ 6.385 rod but not real common for daily drivers. Yes it can be done. Is it recommended? No.

Like we pretty much confirmed until you could actually identify what block and internals it's hard telling what it is.

If I wanted that boat I'd price it intending on new power and rigging and collect what I could for that heap sitting in there. The rigging is aweful and no respectable loving boat owner would let that happen. But let the fun continue...

That is a stock 7.4 MPI mercruiser with stock Oval port heads and Intake with the plastic removed. Its not a mag. The mag has the Rec port intake with the Air intake turned to the side. Turned to the starboard I think.

Chris

mefi 1 ecm = old

what ?

Wai a minute before you answer that. I have to shoot up with something or lick some paper tabs first before I hear the answer,

Hi Chris, thanks for your feedback. I'm a newbie, so I just assumed all Mercruiser big blocks where Magnums? I got that from this page:
https://www.perfprotech.com/blog/boa...marine-engines

When they get to the section discussing the L29, the subtitle is "Mercruiser 7.4L Magnum MPI (L29) Models"...and below they show a photo of the mystery engine that this thread is about.

I've read some other forums and there seems to be lots of confusion as to what is a Magnum, as apparently, Mercruiser would also put the "Magnum" badge on some 330HP motors, not just the 385HP.

So confusing....however, I will say that the engine covers that are missing from this L29 do NOT say "magnum" on it. So going by that, you're correct, it's not a Magnum then?

I'm a newbie, so I'm not sure what you mean by "rigging". I'm assuming just the cabling and wires? I guess that's considered messy from the photo?

I have no idea what this means.