I'm in love with turbos. I have a twin turbo Cayenne with full custom exhaust, intake, aftermarket diverter valves to hold more boost, and a custom tune and the thing absolutely rips from 2300rpm on up. I get awful gas mileage because I can't stay out of boost. It just puts a **it eating grin on my face every time.

I think there are a couple of things missing from the discussion which surprises me, because this forum is a hell of a lot smarter than me... But the turbo vs. charger idea is a lot older than just the last decade. As plenty of the guys have mentioned with Old late 70's/early 80's Merc Turbo's, Gentry, Gale/Banks, etc. Each system has their pro's and their cons.

Supercharger on small displacement engines
PRO'S:
Immediate down low torque (gets the boat on plane)
Consistent tq curve
unmuffled exhaust and blower whine
Easy to tune due to consistency
CON'S:
Poor fuel efficiency
Higher rebuild rate than comparable turbo app
More internal wear due to constant boost
Compressor surge (can sound cool, but often hurts driveability/docking

Turbo on small engine
PRO'S:
Great fuel efficiency due to low boost at lower RPM's
Ability to make much exponentially more power than NA
Less parasitic loss than a belt driven charger (yes there is SOME loss)
Generally quieter
External Blow off valves sounds SAHWEET
CON'S:
Low rpm lacks planing tq
Generally quieter
Tough to water cool effectively (thus far)
Tougher to tune
High RPM for a long period of time can be disastrous (this applies somewhat to chargers as well)
Exhaust Gas Temperature (EGT) management is an issue for high RPM apps

Big displacement motors are a different ball game entirely. Often times they have the exhaust pressure to spool turbo's almost immediately and even if they do not, the big cubes provide the tq down low to get a boat moving. They still are tougher to tune(not a real big deal for modern tech and shops like chief, Mercury, etc), and also to cool. Plus the ultra high RPM of the compressor wheel combined with EGT's, creates issues of it's own. But this doesn't inherently give the advantage to Superchargers. As many have discussed, their linear tq curve, tunability, and killer sound are all big pro's. The constant boost puts more wear on the motor, hurts fuel economy, and seems to require a bit more maintenance. So there are challenges either way. One mistake made earlier in this thread, was comparing boat and car motors. Boat motors run at a constant rate and full drag so to speak (brain fart, can't think of the proper term), were as car motors can cruise more efficiently due to less drag (air vs. water). Once you throttle a motor below full boost, you get into fuel saving territory, and when you want the power, mash the loud pedal and voila!

My theory on the Merc 1350 & 1650's, is that the motor presents not only an ultra high HP package, it does it in almost a luxury manner. Slighter quieter due to turbo's, less engine wear due to varying boost, neat package due to extensive engineering, slim MPG advantage, warranty, etc. One thing I failed to mention, is that turbo's seem, to me, to do a slightly better job of making power with more mild cams. This creates an ease of driveability and docking that many big cube/hp blower motors seem to lack. Okay I'm done now haha

Blower Surge is a thing of the past, unless you are using old style roots blowers. Whipples have zero blower surge.

This is a really interesting read. I have experience with both Turbos and Superchargers and as so many have said both have their strengths. I am no engineer but have been involved in motorsports all my life and in my youth built a lot of motors....That said, I am so impressed with the power capabilities and manners of the 5 litre Whipple blowers on my Teague engines. Very impressive power capabilities of these blowers on low boost levels so they must be pretty damned efficient..... The fact that a serpentine style belt can drive these huge blowers at 12 lbs of boost tells me that they must not require much to turn them....

Even 4.0/5L set up's? That's cool

My old B&M megablower had a lot of surge too,but my engine builder took the time to set it correct on the idle mixture ,and my blower surge was gone ,even when shifting in and out of gear in the marina with a large pitch prop was not going to start surge anymore ... and plumbing the intercooler with its own water pick up thru force feeding is a good idea.

Valve Train is better now days...And if we are only discussing valve train at the moment.

Turbo engines have always lasted longer than Blower engines.

One of many reason's is balanced pressure, with a turbo you have balanced pressure on both the Exhaust and Intake side.

Blowers you are only putting pressure to one side hence blowers also being very hard on valve train.


With out the balanced pressure and the flutter that occurs it is really hard on valve train.
Turbo's clean that up.


Jon

It was my understanding that the expanding exhaust gas is what makes turbos spin?

Is the merc a variable vane turbo?

Yup. Even our 1500 package with QuadRotors (In carb form...) idles like a dream.
Even better with EFI

I have had the pleasure to run with a friend who has twin 565s' with Moonyham blowers and twin carb setups. I have watched him work with jetting and power valves to get those beasts to purr without any great surge. The setup is easy to dock and shifts in and out of gear (wet #6s') without stalling. And from what he has told me the motors run a mild cam and still produce great power. We ran out of lake last year testing props at 160.7 mph and climbing with slip #s' under 10% with 18x41 labbed to death thin Herrings @6000+ rpm.
Technology has come along way and some have learned alot in the process some haven't. This has been my first experience with blower motors and it has been a BLAST! And a BOOM on more than one occasion. Lol