Neither the 3868719 (Volvo Penta like number) nor the T0820479 (OMC serial number) come up in
the system, which is not that surprising as OMC records are a bit sketchy, but the two numbers
show that what you have is one of the “joint” outdrives dating from when Volvo Penta used to
make the outdrives for OMC.
If the engine and drive do date from 1997 or 1998 you have an SX-M 1.5:1 ratio drive. This was
sometimes called a Cobra SX or an SX Cobra. Volvo Penta made the drive for OMC, but made
an identical one for themselves called the Volvo Penta SX-M.
If the age of the engine and drive is really 1996 or 1995 then you have a SX-C 1.5:1. This also
was called the Cobra SX. It is almost the same as the SX-M but it has double cavitation plates
where the lower unit joins the upper unit versus the SX-M which has just one plate.
However, all the inside parts on both the SX-M and the SX-C supersede to the same part numbers
and the transom shields of the SX-M and SX-C while not exactly identical can take either
drive with most of the part numbers super ceding again to the same numbers.
As your SX ratio is 1.51, chances are that you have either a fuel injected 5.7 or 7.4 GM based engine.
OMC used the 5.7, 7.4 and the 8.2L engines in 1998, but didn’t use the 8.2 engine in 1997.
My guess would be that you have a 1997 7.4L engine with a 1997 SX-M 1.5 outdrive.
Or if not the 7.4L then you have a 5.7L although most times they used the 1.60 ratio.
In 1996, OMC used GM 5.7 and 7.4L engines and a Ford 5.8L block. I have seen quite a few of the
Ford blocks use a SX-C 1.5:1 outdrive.
If you can get me any part numbers off the engine, I should be able to ID it for you.
Volvo Penta supplied most of the parts for the engines as well during the joint venture.