400-800 Tru-Coarse steering for or upper gear case will be required in most cases.
There is a left
or right handed worm gear and 1/4 moon gear in most upper cases.
Unit that do not require gears
may have a steering arm attached to the exhaust housing.
If you have twin engines only one will
need steeling and the other will be linked to it.
Most left hand worm gears in upper gear case
are used with power steering applications or steering wheel in 2 location on the boat.
gears for 400/800 upper units 1967 to 1986
There are 2 main types of ball gear and
there is a way of making them interchange. The shaft that holds the ball gear and the drive gear can be changed out.
The shaft is listed under OMC used parts and is also listed on ball gear page. Bearing for both type of shafts are
the same and can be changed over.
Note there is a video showing the shaft being changed over.
Ball gears made in 1967 thru 1969 for 4 cylinder unit with 5/8 or so bore can not be change over but are still in
stock at time of writing.