How Do I Replace My Shift Interrupt Switch
Models
See the following Mercruiser Parts chart
SituationÂ
The following switches are being made NLA: 39670A10, 39670A23, 39670A28, 39670A38, 39671A 3, 49646A 2, 87-806702A 3, 87-19752A 3 & 87-19752A 6.
Correction
There has been two new Shift Plate Kits developed to replace some of these switches. At this time, there are no replacements available for the 39670A10, 39670A23, 39671A 3 & 49646A 2 switches.
Part Required
Order Shift Plate Kit P/N 864363A 1 if replacing the 39670A28 / 39670A38 / 87-19752A 3 / 87-19752A 6 switches. Please see the chart below to determine if this Shift Plate Kit will work for your specific application.
Order Shift Plate Kit P/N 864364A 1 if replacing the 87-806702A 3 switch.
| Model | Serial # Range | Switch Used | Replacement | Original Switch Mounting Location |
|---|---|---|---|---|
| IA/IB/IC EZ Shift Drive | 1776349 thru 2065189 | 39671A 3 | None | Transom Mount |
| 120/140 Drive | 2062141 thru 2791956 | 39671A 3 | 864363A 1 See Note 2 | Transom Mount |
| 120/140 Drive | 2062141 thru 3780849 | 49646A 2 | 864363A 1 See Note 2 | Transom Mount |
| 120/140 Drive | 3780850 thru 6225576 | 39670A28 | 864363A 1 See Note 2 |
Transom Mount |
| 120/140 Drive | 4893635 & Up | 39670A22 | 864363A 1 See Note 2 | �Transom Mount |
| 160 Drive | 2065190 thru 2763441 | 39671A 3 | 864363A 1 See Note 2 | Transom Mount |
| 160 Drive | 2065190 thru 2763441 | 49646A 2 | 864363A 1 See Note 2 | Transom Mount |
| 165 Drive | 2763442 thru 3780849 | 49646A 2 | 864363A 1 See Note 2 | Transom Mount |
| 165 Drive | 3780850 & Up | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| 165 Drive | 4890460 & Up | 39670A22 | 864363A 1 See Note 2 | Transom Mount |
| 470 Drive | 4208730 thru 6225576 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| 485 Drive | 4893835 & Up | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| MC-II Drive | 1602186 thru 2278488 | 39670A28 | None | Transom Mount |
| MC-II Drive (1.78:1) | 2398798 thru 2671321 | 49646A 2 | None | Transom Mount |
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Part Required (continued) Shift Interrupt Switch Replacement Information (continued)
| Model | Serial # Range | Switch Used | Replacement | Original Switch Mounting Location |
|---|---|---|---|---|
| MCM 120/2.5L | 6229718 thru 0C853255 | 39670A28 | 864363A 1 See Note 1 | Alum Rocker Cover |
| MCM 120/2.5L | 6229718 thru 0C853255 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 140/3.0L | 6229718 thru 0C856558 | 39670A28 | 864363A 1 See Note 1 | Alum Rocker Cover |
| MCM 140/3.0L | 6229718 thru 0C856558 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 3.0L/LX (EST Ign./ Conventional/Digital Ign.) | 0C856559 thru 0F603999 | 39670A38 | 864363A 1 See Note 1 | Alum Rocker Cover |
| MCM 3.0L/LX (EST Ign.) | 0F604000 thru 0K999999 | 87-19752A 3 | 864363A 1 See Note 1 | Alum Rocker Cover |
| MCM 165/3.7L | 0B434941 & Up | 39670A28 | 864363A 1 | Shift Plate |
| MCM 170 | 6916779 thru 0B434940 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 180/3.7LX | 0B436391 & Up | 39670A28 | 864363A 1 | Shift Plate |
| MCM 190 (4 cyl.) | 6916779 thro 0B436390 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 470 | 6218037 thru 6916778 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 488 | 6170297 thru 6916778 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 175/4.3L | 0B527955 thru 0F000877 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 185 (V-6 / 229 cid) | 6330183 thru 6919655 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 185 (V-6 / 262 cid) | 0A331455 thru 0B527954 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 205/4.3LX | 0A331455 thru 0F001219 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 262 Mag TBI (Gen +) | 0F803800 thru 0K999999 | 87-806702A 3 | 864363A 1 | Shift Plate |
| MCM 4.3L | 0F000878 thru 0F802999 | 87-19752A 6 | 864363A 1 | Shift Plate |
| MCM 4.3LX | 0F001220 thru 0F803113 | 87-19752A 6 | 864363A 1 | Shift Plate |
| MCM 4.3LX (Gen +) | 0F803800 thru 0K999999 | 87-19752A 6 | 864363A 1 | Shift Plate |
| MCM 4.3LXH (Gen +) | 0F803114 thru 0K999999 | 87-19752A 6 | 864363A 1 | Shift Plate |
| MCM 225-S (Ford) | 3385721 thru 4166999 | 39670A23 | 864363A 1 See Note 2 | Transom Mount |
| MCM 888 (Ford) | 3108723 thru 3777489 | 49646A 2 | 864363A 1 See Note 2 | Transom Mount |
| MCM 888 (Ford) | 3777490 thru 4887829 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| MCM 233 (Ford) | 4173000 thru 4902304 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
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Part Required (continued) Shift Interrupt Switch Replacement Information (continued)
| Model | Serial # Range | Switch Used | Replacement | Original Switch Mounting Location |
|---|---|---|---|---|
| MCM 200/5.0L | 6899058 thru 0F600999 | 39670A28 (ring) | 864363A 1 | Shift Plate |
| MCM 200/5.0L | 6899058 thru 0F600999 | 87-19752A 6 (bullet) | 864363A 1 | Shift Plate |
| MCM 228 | 4765100 thru 6218461 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| MCM 228 TR | 4765100 thru 5170008 | 39670A23 | None | Transmission |
| MCM 228 | 6218462 thru 6899268 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 230/5.0LX | 6899269 thru 0F600999 | 39670A28 (ring) | 864363A 1 | Shift Plate |
| MCM 230/5.0LX | 6899269 thru 0F600999 | 87-19752A 6 (bullet) | 864363A 1 | Shift Plate |
| MCM 260 | 4898730 & Up | 39670A22 | 864363A 1 See Note 2 | �Transom Mount |
| MCM 898 | 4762210 thru 6218461 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| MCM 898/228 | 4898730 & Up | 39670A22 | 864363A 1 See Note 2 | �Transom Mount |
| MCM 898 | 6218462 thru 6899057 | 39670A28 | 864363A 1 | Shift Plate |
| MCM 250 | 4768000 thru 4908849 | 39670A28 | None | Transom Mount |
| MCM 260 | 4908850 thru 6218461 | 39670A28 | 864363A 1 See Note 2 | Transom Mount |
| MCM 260/5.7L | 6218462 thru 0F600999 | 39670A28 (ring) | 864363A 1 | Shift Plate |
| MCM 260/5.7L | 6218462 thru 0F600999 | 87-19752A 6 (bullet) | 864363A 1 | Shift Plate |
| 280 TRS | 4176250 thru 4770199 | 39670A23 | None | Transmission |
| 300 Tempest | 6668677 thru 0B430367 | 39670A28 | 864363A 1 | Shift Plate |
| 320 EFI | 0A543604 thru 0C622418 | 39670A28 | 864363A 1 | Shift Plate |
| 350 Mag | 0A635178 thru 0F600999 | 39670A28 (ring) | 864363A 1 | Shift Plate |
| 350 Mag | 0A635178 thru 0F600999 | 87-19752A 6 (bullet) | 864363A 1 | Shift Plate |
| 350 Mag EFI / TBI (Gen +) | 0F800300 thru 0K001508 | 87-806702A 3 | 864363A 1 | Shift Plate |
| 5.7L/LX EFI (TBI) | 0F355305 thru 0K001505 | 87-806702A 3 | 864363A 1 | Shift Plate |
| 330 TR/TRS | 4623115 thru 6083144 | 39670A23 | None | Transmission |
| 454 Mag Alpha | 0A631894 thru 0B785148 | 39670A28 | 864363A 1 | Shift Plate |
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NOTE: 1
For the following models that have the Shift Interrupt Switch mounted to the top of the aluminum rocker cover, an alternate location will have to be selected for mounting the replacement Shift Plate Kit. Â
MCM 120/140 S/N 6229718 thru 0C856558 MCM 3.0L/LX (Conventional / DIG.IGN. / EST IGN.) 0C856559 thru 0F603999 MCM 3.0LX 0F604000 thru 0K999999
NOTE: 2
The models listed following have the Shift Interrupt Switch mounted either on the Transom Plate or on a shift plate assembly attached at the top of the inner transom plate, with the hydraulic reverse lock valve assembly. An alternate location will have to be selected for mounting the replacement Shift Plate Kit.
Also a new trim pump will be required updating from the old Prestolite trim pump to the new high pressure low flow Oil Dyne trim pump, part number 93247A 7. The new trim pump has the reverse lock valve in the pump and will replace both the pump and the reverse lock valve assembly, for replacement of the trim pump follow the instructions that come with the new trim pump.
| Model | Serial # Range |
| 120/140 Drive | 2062141 thru 2791956 |
| 120/140 Drive | 2062141 thru 3780849 |
| 120/140 Drive | 3780850 thru 6225576 |
| 160 Drive | 2065190 thru 2763441 |
| 160 Drive | 2065190 thru 2763441 |
| 165 Drive | 2763442 thru 3780849 |
| 470 Drive | 4208730 thru 6225576 |
| 485 Drive | 4893835 & Up |
| MCM 225-S (Ford) | 3385721 thru 4166999 |
| MCM 888 (Ford) | 3108723 thru 3777489 |
| MCM 888 (Ford) | 3777490 thru 4887829 |
| MCM 233 (Ford) | 4173000 thru 4902304 |
| MCM 228 | 4765100 thru 6218461 |
| MCM 898 | 4762210 thru 6218461 |
| MCM 260 | 4908850 thru 6218461 |
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