The Boat Doctor
PHOTO: COURTESY AUTOSERVICECOSTS.COMI had a marina do a full inspection
before I bought it. The compression
was great, and the engine computer
reported less than an hour at more
than 4,000 rpm, with the bulk of
the hours near idle. Should I
be concerned?
Second, I noticed that with this
boat, I could hear more engine exhaust
noise than on my previous boat,
which was a Chaparral. After closer
inspection, I noticed that an exhaust
bellows was not installed between the
outdrive and the transom. After some
research, I learned that something
called an exhaust tube was installed
instead. The exhaust tube does not
seal to the outdrive, which allows
exhaust and noise to escape above
the water. Why was this installed
at the factory rather than a bellows?
Is there any drawback to installing a
bellows connection?
Finally, I keep the boat on a lift
in relatively shallow water, which
necessitates that I drive the boat
on and off the lift in the full,
trim-up position. Every time I
perform this maneuver, I ask myself
why manufacturers do not use CV
joints rather than the old-school
universal joints. Can you tell me why
they are not used in outdrives?
CHARLES LINDE
Oshkosh, Wisconsin[ A ] Depending on how hard you use
the boat, the 6.2L will burn some oil.
To be on the safe side, drain the oil and
fill the system with the Quicksilver
25W-40 that MerCruiser recommends
for the engine.
Regarding the exhaust tube,
it’s used on the 6.2L and larger
MerCruiser engines to help get theengine rpm where it needs to be when
the boat is running at speed. When the
drive is trimmed all the way in, it
keeps the sound down; when the boat
is being run at higher speeds, the
exhaust tube lets the engine breathe
more freely than the bellows. You
could put on a bellows without hurting
anything, but it might restrict rpm at
wide-open throttle.
Finally, when it comes to universal
joint versus CV (constant velocity)
joint, the overriding factor is cost.
The CV joint is more expensive; the
universal joint has proven to be a