Mercruiser Alpha One lower unit parts drawing Lower gearcase housing exploded view component drawing 1 - 25 Mercruiser and Alpha One (up to 1990) exploded view lower unit drawing

Water pump components, impellers, seals and shafts

Manufactured by GLM, California. All parts include a 2 year warranty

Easy to identify photos with OEM Mercury numbers Photo Description / OEM # Price

(USD) Price (Canadian) 12120 Water pump Item A

P/N 12120 Complete water pump kit (1984 - 1990, MR and Alpha One, serial numbers 6854393-OD469858). Click on picture for older MC-1, R and 1991 and up Gen 2 models. $35.95 $46.95 51220 GM manifold Item B

P/N 51220 GM 4.3L V6 exhaust manifold, center rise for 1986 and up models. Click on photo for all other engine / model manifolds.



99746A17 $218.95 $288.95 SEI Marine Mercruiser Lower Unit 1623-8951A43 Item C

SE106 Aftermarket



OEM 1623-8951A43 Aftermarket SEI lower unit Mercruiser / Alpha One Gen 1 complete lower units. For 1970 - 1990 models, serial numbers 2791957-OD469858 with 13 spline vertical driveshaft, for up to 300 horsepower.OEM 1623-8951A43 $1125.96 $1499.96 12410 Housing Item 1

P/N 12410 Upper water pump housing (1966 - 1990)



#46-96148T1 $29.00 $36.00 Item 2

P/N 12810 Pump cup (included in upper housing and in P/N 12110 and 12120)



#48752 $5.00 $6.00 89840 Impeller Item 3

P/N 89840 Impeller (1966 - 1990)



#47-89984T4 $15.00 $19.00 21720 Item 4

P/N 21720 Washers (3 units) 12-36001 $4.00 $4.00 12821 Screw OEM 10-30720 Item 5

P/N 12821 Screw 12-36001 $4.00 $4.00 21180 Item 6

P/N 21180 Lock nuts (5 units) 11-35888 $7.00 $8.00 12830 Seal Item 7

P/N 12830 Seal 26-38970 $4.00 $4.00 12820 Tube guide Item 8

P/N 12820 Tube guide 23-29804T $4.00 $4.00 81160 O-ring Item 9

P/N 81160 O-rings (5 units) 25-30613 $4.00 $4.00 21190 Lock nuts Item 10

P/N 21190 Nut (5 units) 11-826709111 $9.00 $11.00 21490 Washers Item 11

P/N 21490 Washer (5 units) 12-29245 $6.00 $7.00 11070 Key Item 12

P/N 11070 Key 28-56654 $4.00 $4.00 31020 Gasket Item 13

P/N 31020 Gasket 27-858524 $4.00 $4.00 12510 Wear plate Item 14

P/N 12510 Wear plate 32435-1 $4.00 $4.00 31010 Item 15

P/N 31010 Gasket 27-85608-1 $4.00 $4.00 12310 Base Item 16

P/N 12310 Water pump base (1970 - 1983 only) 46-57234A1 $25.00 $31.00 85040 Oil seal Item 17

P/N 85040 Oil seal 26-16977 $8.00 $11.00 85070 Oil seal Item 18

P/N 85070 Oil seal 26-89238 $9.00 $12.00 82260 O ring 25-33145 Item 19

P/N 82260 O-ring (5 units) 25-33145 $7.00 $9.00 31040 Item 20

P/N 31040 Gasket 27-856704 $4.00 $4.00 21570 Roller bearing Item 21A

P/N 21570 Bearing (1970 - 1983 only) 31-53079A1 $23.00 $28.00 21580 Item 21B

P/N 21580 Bearing (1984 - 1997 only) 31-36387A1 $32.00 $40.00 23300 Shims Item 22

P/N 23300 Shim 15-57007A1 $6.00 $7.00 21800 Item 23

P/N 21800 Washers (5 units) 12-29395 $5.00 $6.00 30010 Item 24

P/N 30010 Washers (5 units) 12-31266 $4.00 $4.00 85581 Oil seal Item 25

P/N 85581 Oil seal 26-816464-1 $7.00 $9.00 Mercruiser stern drive parts 26 - 50