mcollinstn

AthOR,

Sorry dude, but the 6.2 is a 350 bore and a 400 crank (or at least the same STROKE as a 400). 6.2 has forged crankshaft - most 5.7's have cast nodular iron cranks.

The 6.2 will be torquier than the 5.7 if all other components similar.

hp to $$ favors the 5.7 for sure.

AthORiTAH

UMMM...Sorry Mco.... a 383 is a 350 with 400 crank.
A 6.2 or 377 mag is a destroked 400.
but don't take my word for it. www.speedomotive.com

HippieCustoms

Can I add my 2 c's? Actually I think Mco is correct.. 6.2 is a 4.00 bore by 3.75" stroke. that is 350 bore 400 stroke. The very popular 383 is actually 4.030 bore by 3.75 stroke. The over bore is what makes up the extra 6 cubes. I found some specs on the 6.2 at outdrives.com. I will try to add a link....http://www.outdrives.com/merc/mx62mpi.html

wwwTOPDJcom

mcollinstn
is correct

traviss

The 377 Is a standard bore 350 4.000" bore with a 3.75" crank.. Plain and simple.. I beleive they run "hypertutectic" (Spelling) pistons.. In my opinion I would swtich over to forged if its not already done..

my .02

jafo

I think you will be miles ahead using the 350 - as stated before, they are much less expensive to replace if a failure occurs. I really don't think that the cast vs. forged issue, or for that matter the 27 extra cubes are going to make that much difference- the 350MagMPI is a pretty good piece.....
If out-of-the-hole perf is an issue, you'd be better off with the WhippleCharger. A 350MagMPI with that kit has almost identical numbers in hp and torque to an HP500EFI, and I don't think damage to the Bravo drives would be an issue with that setup.
I would love to do this to my 28' AT!!

mcollinstn

AthOR,

I'm not trying to ruffle your feathers, but I couldn't give a flying twirlyjig what speedomotive has to say. We are talking specifically about Merc motors in the specific flavors, states of tune, and component content as we find them bolted to the stringers of boats. Not cars. Not the world of aftermarket. And not the world of .030 over rebuilds.

And under those conditions, the 6.2/377 package we are talking about uses a standard 4.000" bore.

I don't make the motors for Merc. I am just shooting as straight as I can.

peace.

rmbuilder

AthORiTAH,
Hope this helps,

377 cid custom aftermarket (big bore 400 block .030 over)
4.155 bore x 3.48 stroke

Mercruiser 377 cid prod (std bore 350 block) Scorpion 6.2
4.00 bore x 3.75 stroke

383 cid custom (350 block .030 over)
4.030 bore x 3.75 stroke

383 cid prod (std bore 350 block) GM crate engine
4.00 bore x 3.8 stroke
Bob

Ric232

It's not the cubes. It's the leverage provided by the longer stroke. Think of it this way, the stroke is roughly 8% longer in a 377 vs 350. Let's pretend you and your buddy (who weigh exactly the same, i.e. the cylinder bore is the same size) hop on a teeter-totter where your are both 6ft from the fulcrum point (center). That's equilibrium. If you back up 6 inches and your buddy stays in the same place, your azz is going to hit the ground hard every time.

The only downsides are:

1. The piston is moving faster in a 377 at the same rpms. This is taken care of by using the forged crank.

2. There is some additional side loading in the cylinder due to the longer stroke. I have no idea how much of an impact this has on longevity.

jafo

Side loading and piston speed have a huge effect on reliability especially when running turbo or superchargers. The 6.2 may make a little more power, but will not have the same TBO as its shorter-stroked brother.
It would be much easier to stomach buying a 350 than 6.2 if you grenaded one- Merc is real proud of their stroker engines, especially the Scorp. You could have Lingenfelter of Pfaff put one together for you for what Merc gets, maybe even for a little less.