Procharge 350Mag vs 6.2
 

On a Formula 292 (current hull design) which power plants are the better candidate for pro or whipple chargers - the 350Mag or the 6.2's?

I don't have a technical answer for you, but I would say the 350...
A lot less $$ to replace one when it blows up.

Good point!

There is not much difference in these engines. They share many of the same parts.

the 6.2 is a 377. go with the cubic inches...

I believe the 6.2 has a much stouter bottom end.

A buddy procharged his 6.2's in his 292 formula fast tech. These boats are a biatch to get on plane and worse after prochared beacuse of the larger props. You're going to want as much low end torgue as you can get. I think the 6.2 are tourqier(is that a word:D) than the 5.7. I'd go for the 6.2's

Brian

Thanks for the insight Caincando1

So your buddy wouldn't go that route again? Perhaps 377 Scorpions are the better choice normally aspirated.

if you procharge the 6.2 you will need an oil cooler and a larger oil pan. the 6.2 is really lacking in the oil pan area and has no oil cooler

I believe either are equil canidates, I don't know if the 6.2 is more "stout" in the bottom end, but I can tell you
that it's nothing but a destroked 400 and uses a 350
crankshaft. They are both well balanced engines, but
hp to $.....the 350 would be the better choice. In a procharged application you wouldn't notice much differance. I also agree, a larger oil cooler would be
a good idea, especially if you plan on running the boat hard.

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.

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

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

mcollinstn
is correct

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

my .02

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!!:)

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.

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

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.

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.;)

The 6.2 is a better motor because it has lower compression and you can run safely 6-8psi vs. 4-5psi on the 350mag. 6.2 will also make about 50-60lbs of torque more at low and mid rpm ranges. Both the 350 and 6.2 could really use a larger capacity oil pan (stock is 4qt) and an oil cooler if supercharging.

Dustin

Thanks for the info! Great forum.

Just for the record the 6.2 uses a forged Lunati 3.75" stoke crank and forged dished pistons to achieve a 9:1 compression ratio. The cam is more aggressive than the 350 Mag. It has the exact same specs as a Crane 104224, but there are no markings on it to identify that Crane made it. It is also internally balanced. Other than that the 2 engines are identical. Ironically, they both use a 2 bolt main block!

Sometimes you have to just be patient and the guys who really know come out to play (Dustin and bobl).

Thanks.

I confess- I quit playing with pistons engines about 20 years ago--way too many parts trying to beat their way out. I just own and drive them any more.... I'm strictly a turbine guy. :D
But, I'll take a pair of each (but forget the 6.2, I want the Scorps);)