Bravo III: Spinning Wheels or Making Progress?
been an eventful year since BoatUS first asked MerCruiser
to explain why its twin-propeller Bravo III outdrives seem
prone to corrosion damages. For one thing, 328 owners have
reported to BoatUS that their outdrives are pitting, crumbling
and deteriorating to the point of needing repairs. For another,
while steadfastly denying there’s a problem with its
outdrives, MerCruiser has issued a service bulletin describing
an elaborate protocol of tests to determine why Bravo IIIs
BoatUS has received few reports about corrosion damage on
single-prop MerCruiser outdrive models and none involving Volvo
outdrives. Volvo Penta is the only other manufacturer producing
outdrives with two propellers. Most of the Bravo III complaints
in our files involve 1998, 1999, 2000 and 2001 models.
If there is a formula for success in dealing with MerCruiser
it is to follow their instructions to first have an authorized
mechanic inspect the boat at its normal mooring place. This
will help the mechanic to determine if stray current from the
dock wiring system or from neighboring boats is the source
to MerCruiser’s definition, “Stray
current corrosion is caused by leakage of current into and
the metal drive components, exiting for a water path to ground.
Stray current corrosion is commonly a result of connecting
a boat to shore power.”
other hand, galvanic corrosion, which is a reaction between
metals, seems to be at the crux of the
MerCruiser Bravo III problem. Bravo III’s design features
two large stainless steel props, an aluminum housing and aluminum
MerCruiser’s bulletin explains, “the simplest
example of galvanic corrosion, and the most applicable, is
an aluminum lower unit with a stainless steel propeller.” Just
like with the Bravo IIIs.
just discovering crumbling skegs and drive housings are keeping
crossed that damages will be covered
by MerCruiser’s three-year corrosion warranty. They have
good reason. Others who are not so lucky report spending well
over $5,000 for replacement outdrives. MerCruiser will not
help if damages are caused by outside sources and only on rare
occasions will they help if damages occur after the warranty
maker has a few recommendations for lessening the chance
will happen. Using the right type of
sacrificial anode is crucial. Merc produces aluminum anodes
for use on boats kept in salt water and magnesium ones for
use in fresh water. Trouble is, not many boat owners and few
MerCruiser mechanics knew about these special anodes until
a few months ago. Many boat owners learned the hard way that
zinc, the traditional anode material, doesn’t afford
adequate protection for Bravo III outdrives in any environment.
MerCruiser also recommends using its Mercathode system to
suppress galvanic current between aluminum and stainless steel
components. However, whereas once only a single Mercathode
per engine was needed, now the engine maker recommends installing
company have plans for new components or design modifications
prevent galvanic corrosion altogether? MerCruiser isn’t
Are owners getting any help when they bring their corroded
outdrives in for repair? Yes, to a limited extent. The logjam
seems to be breaking, but mostly on units still under warranty.
Does BoatUS want to hear from Bravo III owners who either
are experiencing problems or who have been helped by MerCruiser?
Definitely! Contact the Consumer Protection Bureau at 703-461-2856
or by e-mail, ConsumerProtection@BoatUS.com.
BoatUS Magazine, September 2002
article is a follow-up to Corrosion
Burns I/O Owners and
Erodes as I/Os Corrode**