MerCruiser TR / TRS

Drive specs

Specifications for MerCruiser TR / TRS
Model years	1973–1993
Type	Drives

Drive specs
Upper gear unit	No gearbox in the drive; reverse gear in the boat
Propeller system	Single propeller

Variant	Gear ratio	Year	Identification	Source
TRS right-hand (RH)	—	1973–1993	Serial number from 3377316; lower unit 5321A6; propeller approx. 14–16 in, propeller nut 1 1/16 in	Sterndrives.com: drive table with serial numbers and gear ratios (sterndrives.com) MerCstuff: identifying TR/TRS (external link)
TRS left-hand (LH)	—	1973–1993	Serial numbers from 3377316	Sterndrives.com: drive table with serial numbers and gear ratios (sterndrives.com)
TR	—	1973–1993	Larger lower unit than the TRS; removable rear cover with 4 bolts, like the TRS	Sterndrives.com: drive table with serial numbers and gear ratios (sterndrives.com) MerCstuff: identifying TR/TRS (external link)

Sterndrives.com: MerCruiser Sterndrive Chart (years, serial numbers, gear ratios) (sterndrives.com)
sterndrives.com · HTML · 2004
R/MR, Alpha One, Gen II and Bravo I/II/III by serial number range. Always check both the upper and lower gear sets.
Mariner's Warehouse: How to identify a MerCruiser outdrive (Alpha One, Gen II, Bravo) (marinerswarehouse.com)
marinerswarehouse.com · HTML
Visual differences between generations and where the serial plate is located.
MercruiserParts: Where is my serial number (www.mercruiserparts.com)
www.mercruiserparts.com · HTML
Serial number locations on engine, transom plate and drive.

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Mercruiserparts.com: exploded views (Mercury parts catalogue) (www.mercruiserparts.com)
Exploded views by serial number
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Crowley Marine: MerCruiser OEM exploded views (external link)
Search by drive serial number

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Drives

1967–1990

Drives

1984–1990

Drives

1991–

Drives

1988–