Stern Drive Info

B l u e S p r i n g s M a r i n e 3 2 0 0 N W J e f f e r s o n S t r e e t B l u e S p r i n g s , M O 6 4 0 1 5

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For over 50 years, Blue Springs Marine has provided assistance to the boating community in the purchase and servicing of their boats and motors. Our knowledgeable staff of experienced boating enthusiasts has over 200 years of combined boating and industry experience. When contemplating and planning your boat purchase, openly discuss your needs and expectations with your salesperson. There is never a silly question. Gathering factual information and cultivating honest opinions is paramount in determining the products that will best fit your needs and budget, and ultimately making the best informed buying decision you can. The information shared below is an attempt to provide a conscientious and honest response to some common issues in hopes that you are better informed.

STERNDRIVE PROPULSION INFORMATION PROPULSION MANUFACTURERS

There are two manufacturers of sterndrive propulsion systems - Mercruiser and Volvo Penta. Independent manufacturers such as our Chaparral line use both. The boat building divisions of Brunswick Corporation including our Bayliner line use Mercruiser sterndrives exclusively. Here in our mid-west market area, Mercruiser has the larger market share. This is mainly due to a larger number of Mercruiser oriented dealerships and authorized service centers. Mercruiser is very predominant across the state, and particularly so at Lake of the Ozarks. Volvo has a healthy market share particularly in the southern Missouri and Table Rock lake area. Some independent boat brands are heavily oriented towards Volvo including Cobalt. Stingray relies solely on Volvo. Sea Ray is a Brunswick company, therefore exclusively Merc. Rinker and Crownline are independent builders but use Mercs exclusively. Blue Springs Marine routinely services both brands. We typically stock our Chaparral boats with Mercruiser powertrains. Volvo is always available on a custom order per your specifications and preferences.

CATALYZED MOTORS

Since January 2010, the US EPA has required that all marine sterndrive engines be equipped with catalytic converters, with the initial exception of 3.0L and 4.3L powerplants. The caveat being the non-catalyzed 5.0L, 5.7L and 8.1L that had been produced and still in the supply pipeline could still be installed after Jan 2010. Our Bayliner boats still have a reasonably healthy supply of non-catalyzed motors available for installation. Chaparral, on the other hand, has very limited non-catalyzed motors available after January 01, 2011. There is of course good reasoning behind the EPA mandate with the environmental benefits topping the list. The new catalyzed motors will have a dramatic reduction of CO emissions and much less exhaust odor, however, there are cost implications as well so be prepared for higher prices. Absolutely no boat, newly registered in the State of California after Jan 2010 can be non-catalyzed.

POWERPLANT OPTIONS

Both Mercruiser and Volvo marine gas engines are marinized utilizing General Motors blocks. Displacements include:


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Engine-wise the two brands are comparable. Some areas where a particular brand shines:

3.0L (181ci) I-4 Mercruiser seems to own this market segment. TKS (Turn-Key-Start) carbureted versions and the new catalyzed MPI version are both rated at 135hp.

4.3L (262ci) V-6 Both Mercruiser and Volvo offer good motors in this displacement. Carbureted versions are each rated at 190hp. Mercs MPI version is rated at 220hp where Volvos MPI is rated at 225hp.

5.0L EFI (305ci) V-8 Volvo is rated at 270 HP rather than Merc's 260, both are good motors and price comparably.

5.7L EFI (350ci) V-8 Both Merc and Volvo have 5.7L MPI catalyzed 300 HP motors, with the Volvo pricing somewhat lower. You can also get Volvo's 320hp 5.7GXi High-Output.

6.2L EFI (377ci) V-8 The 6.2L is only offered by Mercruiser. It is rated at 320hp and is pricey. Compared with 5.7L to 8.1L or 8.2L big block pricing, most consumers make the jump from the 5.7L and go the route of the big block upgrade, by-passing the 6.2L.

Big Blocks Merc has now moved to the 8.2L (502ci) while Volvo is still utilizing the 8.1L (496ci). Both are fine fuel-inject catalyzed motors. Merc typically prices higher due to the closed-cooling system being standard, optional on Volvo. Merc also has a nice air-actuated quick-drain system that easily purges fresh water from the heat exchanger, water-pump and exhaust manifoldsvery handy in transitional times early and late in the season. Mercs standard output 8.2 is rated at 380hp and their high output version is rated at 430hp. Volvos 8.1L is rated at 400hp.

In General Regardless of the brand, purchase from a dealership closer to where you live or where you will be using your boat; they will be supporting you after your purchase for parts, accessories and warranty.

If you are newer to boating, talk to friends and other folks about the boats they have and the power they have. Find out what they like and dont like. Try to go for a ride with them or demo with your dealer.

Discuss how you want to use your boat and your performance expectations. Openly share information with your dealer so the performance of different powerplants and drive combinations can be discussed and then priced out. Cost/benefit can then be evaluated and your expectation and budget better managed.

OUTDRIVE OPTIONS

Sterndrive powertrains are comprised of two components, the actual motor or powerplant, and the outdrive. Single prop drives comprise the majority of sterndrives on the market today with twin prop drives becoming more popular with the larger and heavier pleasure boats. MERCRUISER Merc offers a wider variety of available drives. For recreational boating applications you will typically see Alpha One single prop drive and the Bravo Three dual prop drive. Both manufacturers offer salt water drives as well which are not included in this discussion.

Alpha One Drive


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The Alpha One drive is rated to handle up to 300hp and up to a 15 diameter prop. It is compatible with 3.0L, 4.3L, 5.0L and 5.7L powerplant displacements.

Bravo One Drives The Bravo One is a single prop drive rated to handle up to 400hp and up to a 16 diameter prop. The Bravo One X is a more robust single prop drive rated to handle up to 450hp and 16 prop. More esoteric is the Bravo One XR single prop drive rated to handle up to 600hp and 16 prop. The Bravo One series drives are very popular for twin engine go-fast powerboat performance applications. Compatible with 5.0L thru 8.2L powerplant displacements, it is typically used with the big-block 8.2L powerplants.

Bravo Two Drives The Bravo Two is a single prop drive rated to handle up to 400hp and up to a 20 diameter prop. The Bravo Two X is a more robust single prop drive rated to handle up to 450hp and 20 prop. The Bravo Two series drives are best suited for single or twin engine heavy load applications such as cruisers or houseboats. Compatible with 4.3L thru 8.2L powerplants.

Bravo Three Drives The Bravo Three is a twin prop drive with counter-rotating props rated to handle up to 400hp and up to a 16 diameter props. The Bravo Three X is a more robust twin prop drive rated to handle up to 450hp and 16 props. More esoteric is the Bravo Three XR twin prop drive rated to handle up to 525hp and 16 props. The Bravo Three series drives are very popular for single and twin engine pleasure boat applications. Compatible with 4.3L thru 8.2L powerplant displacements, they are typically used with the 5.7 and 8.2L powerplants.

VOLVO PENTA Volvo offers two drives, the SX single-prop drive and the DPS Duo-Prop twin prop drive with counter-rotating props.

SX Drive The SX drive is rated to handle up to 320hp and is compatible with 3.0L, 4.3L, 5.0L and 5.7L powerplant displacements.

DPS Drive The SX drive is rated to handle up to 420hp and is compatible with 4.3L thru 8.1LL powerplant displacements. Generally used with 4.3L and 5.0L motors in twin engine cruiser applications, and the 5.7L and 8.1L motors in single-engine pleasure boat applications

IN GENERAL Mercs Alpha single-prop drive still utilizes a mechanical dog clutch vs. hydraulic clutching; Merc Bravo series drives and all Volvo drives utilize hydraulic clutching mechanisms. Hydraulic clutching is generally smoother operating.

Merc has a drive-lube monitor whereas Volvo utilizes a dipstick in the top of the outdrive. Merc has permanently lubricated, no maintenance, U-joints and gimbal bearing. Mercs drive coupler can be greased from inside of the boat without removing the outdrive. Mercs Alpha has the water-pump impeller drive mounted which is typically more expensive to replace than the Bravo and Volvo engine mounted pumps.

Volvos transom assembly allows interchangeability of SX and DPS drives. Merc Alpha and Bravo Series drives are not interchangeable.

Volvo drives tend to be more beefier and robust but generally have more drag coefficient. Volvo utilizes a drive saver coupler designed to protect the transmission by shearing if the propellers strike a submerged object at speed.

Both manufactures have impact kick-up protection, however Mercs system automatically returns the drive to the water to maintain control.

Merc typically has a larger dealer service network for a given geographic area, greater parts availability, and longer recommended maintenance/service intervals.


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WHAT POWERTRAIN IS RIGHT FOR A BOAT?

Generally we recommend the 3.0L with a single prop drive for all around boating in boats up to a 2300 pounds - bearing in mind the lower bottom-end torque. Our Bayliner brand has hydrodynamicaly designed their hulls to perform very well with the 3.0L and 4.3L powerplants.

4.3L and single prop drives are well suited for 2500-3100 pound boats. 5.0L and 5.7L motors are well suited for 3200-5200 pound boats. We typically recommend you strongly consider a twin-prop outdrive in a 22 or larger boat.

8.1L and 8.2L are generally used in boats over 25 and more than 5200 pounds. These motors are most often coupled to a twin prop outdrive. Single prop drive applications with these motors are usually in go fast performance applications.

With each powerplant and drive combination, theres a range of props available for differing applications. Always share with your dealer your performance expectations so your expectations can best be managed.

Both manufacturers offer engine management systems. Merc utilizes a proprietary system they developed called SmartCraft. Volvo offers a similar system they call EVC or Electronic Vessel Control. There are some very nice features built into these systems, including fuel flow & management, outdrive trim, rpm, speed, critical engine operating reading and engine diagnostics. Usually found on larger boats, they are somewhat pricey but well worth it for the right consumers.

FUEL CONSUMPTION

Although there have been changes in fuel consumption figures with fuel injected motors, the following guidelines should be true for engines relative to each other. These figures have been used for a number of years and they seem to bear out:

Engine size 3.0 L 4 Cyl

4.3L V6

5.0L V8

5.7L V8

8.1/8.2L V8

Gallons per hour (Cruise) 3.5

5.5

8.5

10

14.3

Gallons per hour (Avg.) 2.3

3.6

5.6

6.6

9.4

The gallons per hour (cruise) figures are at roughly 3500 RPM, or what we refer to as cruising speed. Fuel consumption, or fuel burn, for boats is usually discussed in gallons per hour vs. miles per gallon.

The Average consumption numbers are calculated at 2/3 of Cruise consumption. This tells you how many gallons a boat will use if it runs so many hours over the course of a season. For example, the 3.0L powered boat will burn 2.3gal x 100hrs=230 gallons per 100 hours of use. Most people use their boat 60-100 hours per year. Fuel consumption numbers go up, rather dramatically above 4000rpm to WOT (wide open throttle). Motors do need to be opened up to WOT periodically, but operation at higher rpms is usually in short durations.

Miles per gallon varies by the speed the boat goes at its' gallon per hour rating. For example, two boats have a 3.0L motor. At cruise, one boat goes 30 MPH/3.5 GPH=8.57 miles per gallon. The other goes 25 MPH/3.5 GPH=7.14 miles per gallon.

Range is another term we use and is related to how far a boat can go on a tank of fuel. Range is typically calculated at cruising speed and 90% of the fuel cell capacity. As an example, a boat with a 4.3L motor burning 5.5gph and a 30 gallon tank, that achieves a cruising speed of 35mph at 3500rpm, will have a range of 172 miles, [(30gal x 0.9)/5.5gph] x 35mph

Based on the figures above on 80 hours of use and fuel at $3.00 per gallon, cost of fuel for a seasons worth of boating is $552 for the 3.0L, $864 for the 4.3L, $1,344 for the 5.0L, $1,632 for the 5.7L and $2,256 for the big block 8.1/8.2L motors.

Information and opinions contained here are based on manufacturers data and specifications, and with our best information and intentions to better inform the consumer.

Documents

Stern Drive Info