Re: 5.0L MPI Supercharger
From an engineering view point:
The drive train is designed for a maximum amount of torgue, for arguments sake lets say 400 lb ft. A 350 (5.7) will get close to that at higher RPMs (3000 RPM and up) but no where near that at say 1000 or 1500 RPM from a WOT hole shot. Lets take you analogy with a big heavy boat and a theroretical engine (diesel?) that cranks out 250 lb ft at 2000 RPM. The drive could handle that load day in and day out without any issues. (Well below the 400 lb ft max.)
Or if you like, go the other way. Your 350 is running at 4800 RPM at WOT and is putting out say 350 lb ft. That is approaching the drives maximum rated torgue and is more likely to fail. It doesn't matter at all to the gears and shafts what the load is, as long as it doesn't cause resistance that would require the engine to input more torque than they are desinged for. As the 350 is not capable of exceeding the maximum input, especially at low RPM, a WOT hole shot does not present a danger to the drive.
You guys are touching on a few different subjects here.
Couple things to keep in mind.
Wear = RPMS Squared.
Ever bog down you're angle grinder that's designed to work at 13000 rpms?
Ever roast a drill bit trying to drill into steel because you're rpms are too high?
The TORQUE being put through the drive is going to effect the PSI between the teeth on the gears.
The RPMS is going to wear them down.
a mathematical formula would look something like this
wear = ( rpms * rpms ) * torque
Chance of sudden catastrophic failure = peak torque
Think of it this way:
300 ft/lbs of torque @ 0 rpms = last forever
600 ft/lbs of torque @ 0 rpms = sheer the teeth of the gears, fail
300 ft/lbs of torque @ 100 rpms = 1,000,000 hours of life
300 ft/lbs of torque @ 1000 rpms = 10,000 hours of life
150 ft/lbs of torque @ 1000 rpms = 20,000 hours of life
300 ft/lbs of torque @ 4000 rpms = 2,000 hours of life.
450 ft/lbs of toque @ 4500 rpms = 400 hours of life..
these numbers are kind of off the top of my head, but you get the idea.
And were not even factoring in heat. which is a whole other variable.
needless to say, supercharging a 305 to 350-400 hp would reduce the alpha's life span and greatly increase it's chances of sudden failure. A tru-hull exhaust would help greatly.
For all the screwing around, if you're boat is slippery enough to be hitting 66 MPH with a 305, you're best upgrade without effectively writing off you're current boat would be a 5.7. Anything more than that, and you're looking at a bravo, which, for all practical purposes means new boat.
with the 5.7, you'd be doing 68-73 or so, and if you wanted to go faster than THAT, you're best bet would be to move away from an IB/OB setup entirely.
