alpha-drive

Mercruiser Alpha Drive

 

bravo3

Mercruiser BRAVO 3


seacore
Mercruiser Sea Core




dps

Volvo DP-S

 


oceandrive

Volvo Ocean Drive

 

volvosx

Volvo SX

Mercruiser or Volvo?

This position paper is authored by Hoffmaster's Marina and is a result of input from potential customers. It is NOT designed to be the final word but rather,
an attempt to provide a conscientious and honest response to some of the
most common issues in hopes that a better informed consumer will be less vulnerable to misinformation. (Updated February 2008.)

Sterndrive Units

There are two brands of stern drives—Mercruiser and Volvo Penta. Cobalt and Chaparral use both. The boat building divisions of Brunswick Corporation use Mercruiser sterndrives exclusively—those builders include Sea Ray, Maxum, and Bayliner. Rinker uses Mercs alone while Stingray relies solely on Volvo. Pretty much every other boat builder uses both brands with Volvo holding
a slightly larger share of the market of the builders using both makes of motor.

Back in the 1980's, Volvo produced its drives in Sweden and parts were not only hard to get but expensive as well. Volvo changed that policy when they developed the SX and Duoprop drives in 1994 and 1997 respectively. The drives are now built in Tennessee. Parts are easily obtainable and competitive with Mercruiser—although still harder to find in after market brands. Volvo has a 72-hour parts guarantee in place and fills orders at over 95% of those requested. To counter the claim that Volvo has less dealers, they instituted a 24-hour service hot line for people to call in with repair requests.

Volvo has an engine-mounted water pump on its drives which according to their instruction manual should be replaced every year. A mechanic can do this for roughly $150. Mercruiser uses engine-mounted water pumps on their Bravo series; the Alphas use a drive mounted pump. According to their service manual, pumps need to be replaced every two years. However, you can expect to pay a yard $375–$400 to replace the impeller on a Bravo drive and $500–$550 on the Alpha. The SX and Duoprop drive impellers are user-serviceable. The water pump on the Bravo is not easy to service and on the Alpha you definitely don't do it yourself. This is not a laughing matter! Read this article for more info: http://www.cgauxinternational.org/news/news5.html.

Volvo SX has cone clutch shifting which is much more positive than the Alpha One's clutch dog shifting. Mercruiser uses the cone clutch shifting on it's BRAVO series drives. Volvo has a drive saver coupler which decreases the cost of repair in case of striking a submerged object. In many cases, damage to an Alpha One prop shaft will damage both the lower and upper gear sets. Many insurance companies won't pay to replace a gear set that visually is okay. The old set goes back in only to fail later and strand the boater. On the other hand, you can strike an object hard enough to pop Volvo's coupler requiring a tow home but with a Merc you might be able to limp home. Mercruiser offers a BRAVO 1 Drive for standard prop sizes and higher top speed, and a BRAVO 2 drive with a very large diameter prop for really heavy boats. I would personally rather have the BRAVO 3 or Volvo Duoprop drive because the prop sets deliver so much thrust pushing the boat onto plane.The Duoprop has patented specially tuned props that deliver more thrust than BRAVO III and with much less cavitation.

In 2007, Volvo updated the Duoprop Drive to the DPS—this was an evolutionary change that addressed many smaller competitive issues with Mercruiser not addressed by this paper. We encountered problems at first with the trim system but that seems to have worked itself out and overall the drive is a big improvement on an already great design. It even seems to be a little faster at the top end.Volvo produces a drive with an external composite case. Although there is still metal inside the drive, the composite takes 90% of the metallic surface away from the water making the new drive very resistant to corrosion. So far we've had excellent results with their new Ocean Drive and recommend it for any application where the additional protection is worth the $1500–$2000 premium over a standard Duoprop.

Mercruiser has introduced a new product called Sea Core. This drive unit takes the approach of using a different metal alloy to prevent corrosion rather than using a composite coating like the Ocean Drive. The corrosion warranty is 4 years. Instead of neutra salt, a chemical engine flush system used by Volvo, Mercruiser uses a fresh water flush fitting (which is standard on all Volvo motors). Our take is that Volvo has a better engine corrosion system with neutra salt—as long as you can also order the motor with enclosed cooling (Sea Core motors all are enclosed). Even though the fresh water flush is good in addition to being environmentally friendly, it’s also a good idea to periodically run a rust inhibitor in areas of the motor that are not in the enclosed portion of the cooling system (the engine is never 100% enclosed even with enclosed cooling). If you want to only flush with water, Volvo offers the flush on every motor where Merc only does on its Sea Core series. For these reasons we tend to stock Volvo Penta drives on our boats although we order Merc powered boats for our customers upon request. The V drive boats we sell run about 50/50 Volvo to Merc.

Power Plants

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

Although there have been changes in fuel consumption figures since the introduction of fuel injection, the following guidelines should be true for engines relative to each other. We have used these figures for many years and they seem to bear out:

Engine size
3.0 L 4 Cyl
4.3L V6
5.0L V8
5.7L V8
8.1L 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

Gallons per hour numbers never change. Miles per gallon varies by the speed the boat goes at its' gallon per hour rating. For example, two boats have a 3.0. 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. These gallon per hour figures are at roughly 3500 RPM. Average consumption is 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 2.3 x 100=230 gallons per 100 hours of use. Most people will use the boat 75-100 hours per year. We feel a person can run a gas motor at 75%-80% at wide open throttle all day long without hurting the motor.

What Power is Right For A Boat?

Generally we recommend the 3.0L for all around boating in a 2300 pound boat—bearing in mind that our customers have complained about the rough idle and weak torque. Use the 4.3L for 2500-2900 pound boats, and the 5.0 or 5.7 for 3000-5200 lb boats and the 8.1 for heavier ones. The 4.3 and V8 motors have better torque for ski take offs. The Duoprop and BRAVO3 model drive are excellent also for this purpose. Fuel Injection provides easier starts and smoother acceleration but also costs a lot more so it ends up being a value choice for the consumer. Mercruiser has a fast start system to try and make the carb motors start faster but we recommend fuel injection over 21'.
You should consider fuel injection in any range.