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History of OMC *800 years 1978-1985 *Cobra 1986-1993

Outdrive history 1978 to 1993 full mechanical lower units
Cobra technical design changes years 1986 to 1993

  • Early models servo hydraulic shift
  • Mechanical shift outdrive
  • 800 and 400 models
  • Exploded View Drawings
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By author Trish Dougherty

In 1977, they discontinued the production and manufacturing of the Stringer – Electric shift model. They opted to keep the upper gear housing design the same as with the Stringer model; and in 1978 completely redesigned the lower unit.

This new design would call for a sliding clutch dog in the lower unit which would engage and lock into the forward or reverse gear.

This clutch was manually engaged by the use of a shift cable which contained 2 inner cores (one or reverse, one for forward). These new models were called the 400 series (4 cylinder engines) and the 800 series (6 cylinder, V6 and V8 motors).

The early models between 1978 and 1981 used a hydraulic oil pump in the lower unit to assist the mechanical shift cable to engage the clutch dog into gear.

In 1982, engineers redesigned the lower unit once again; and designed the out drive to shift with a mechanical shift cable. They removed the hydraulic shift assist pump as they found this wasn’t needed with some of the new shifting components the new design called for.

The units were still called the 400 and 800 series models – but were widely referred to as the ‘mechanical shift’ models. This version of the 400 and 800 series were produced up to the year 1985.

Cobra years 1986 to 1993

The early Cobra models did have some technical design


  • Clutch dog and shift detent updates
  • U-joint system
  • Outdrive parts click here

OMC completely re-engineered their outdrives in 1986 and introduced the Cobra model. Their new modern manufacturing facility was located in Lexington, Tennessee. These new models were available in a variety of motor options; including a 2.3L Ford 4 cylinder (1986-1987), 3.0L Chevy, 5.0L – 5.7L – 5.8L Ford and Chevy small block V8’s and the monster 7.5L 460 Ford big block V8 (1987-1988 King Cobra). The new models no longer used the poorly designed ball gear system and used the modern u-joint style drive system.

The early Cobra models did have some technical design flaws which caused some problems when shifting. The original clutch dog had a 3 degree undercut on the top of the tooth; this angle wasn’t sufficient enough to keep the clutch engaged into the gear in certain instances. The clutch was updated to a 5 degree undercut; and a shift interrupter switch was added.

Along with an updated design for the shift detent – these changed did help with some of the shifting issues the drive may experience. One major difference with the Cobra models compared to the Mercruiser was that when the upper housing and lower gear case were mated together – the oil cavities were connected and an oil reservoir was not needed. The outdrive needed to be filled from the bottom fill plug until the oil reached the dipstick in the top cover of the upper housing.

Another difference was that the water pump assembly and impeller were installed in the upper gear case instead of lower unit.
In 1993, OMC along with Volvo entered into a joint venture and produced a hybrid model knows as the Cobra SX. This new design was all Volvo engineering with the transom being the original design. This hybrid model is also referred to as the ‘cone clutch’ model; the shifting components are heavier duty and no longer used the clutch dog system.

Outboard Motor Corporation officially went out of business in 1998 when Volvo purchased their rights and their manufacturing facility in Lexington. OEM parts are still being manufactured through BRP (Bombardier Recreational Products). Many OEM parts are still interchangeable with Johnson and Evinrude outboard models; and some outboards still use the identical lower housing as the Cobra model.

Click here for OMC King Cobra components