GENERAL
Beginning in 1983
Mercruiser introduced the R/MR/Alpha 1 series of
sterndrive models. These units differed greatly
from previous years not only in design but also
in that the flywheel housing on the engine
changed at this point. This creates one of the
big break points customers should be familiar
with when inquiring about re-powering older
boats. Since the flywheel housing changed from
1982 to 1983, you cannot couple a new engine to
a pre-1983 sterndrive unit as the rear engine
mount spacing differs on the new engine and
therefore will not match to the old style inner
transom plate. The other difficulty is that the
newer 14 inch flywheel utilize a larger coupler
that prevents re-using the old flywheel housing
on the new engine.
The R/MR/Alpha
Generation 1 models began in 1983 and ran
production through 1990. The serial numbers for
these models ranged from 6225577 Thru 0D469858
The Alpha
Generation 2 models were introduced in 1991 and
are currently still in production. The Gen 2
units have been broken into several different
serial number ranges as follows:
1991 thru 1995 - 0D469859
Thru 0F679999
1996 thru 1997 - 0F680000 Thru 0K999999
1998 and Up - 0L100040 And Up
GEAR RATIOS
A very common
question raised when changing outdrives regards
the gear ratio. Mercruiser made the following
gear ratio changes several years ago in effort
to develop s stronger gear combination.
What was a 1.50:1 thru 1995, in
1996 changed over to a 1.47:1
What was a 1.65:1 thru 1995, in 1996 changed
over to a 1.62:1
What was a 1.84:1 thru 1995, in 1996 changed
over to a 1.81:1
What was a 1.98:1 thru 1995, in 1996 changed
over to a 1.94:1
In 1998 Mercruiser introduced the 2.0:1 gear
ratio which has since replaced the 1.94:1
SHIFT LEVER
One noticeable difference
between the Gen 1 & Gen 2 drives is the shift
lever as shown in Figure 2. The old style brass
shift lever will not engage in the Alpha Gen 2
transom assembly and therefore prevents
installing a Gen 1 drive on the Gen 2 transom
assembly.