Water Pump Repair Kit 47-803748-1 3B2-65021-1 for Mercury Tohatsu Nissan 6 8 9.8 9.9 HP Outboard
Water Pump Repair Kit 47-803748-1 3B2-65021-1 for Mercury Tohatsu Nissan 6 8 9.8 9.9 HP Outboard
Product Overview
Water pump repair kit for Mercury, Tohatsu and Nissan 4 stroke outboards from 6 HP to 9.9 HP. It fits and replaces Mercury 47-803748-1, Tohatsu 3B2-65021-1 and Sierra 18-8920, and covers the Mercury 8 HP 209cc blocks as well as the 9.9 HP BigFoot gearcase. The impeller is 6 blades in neoprene with a hardened nylon hub, 40.3 mm (1.587 in) outer diameter, 12.0 mm (0.472 in) hub and 18.0 mm (0.709 in) high. Two gaskets and the drive pin come in the box.
This is the whole water pump service, not just the rubber wheel. The two gaskets are what seal the housing and the wear plate, and an old gasket that has gone hard is why a freshly rebuilt pump still dribbles water into the leg.
The same kit is sold under three families of part numbers because Mercury and Tohatsu built these small four strokes together and the OMC and BRP numbers carried over. All of them are listed below, plus the Sierra aftermarket number.
The kit was also used on the Mercury 47-803748K01 and the Tohatsu 3B2873221M and 3B2-87322-0 water pump assemblies, so if your parts book shows one of those kit numbers the contents are the same.
Specifications
| Specification | Detail |
|---|---|
| Condition | New / New with tags |
| Type | Water pump impeller repair kit |
| Mercury Part Numbers | 47-803748-1, 8037481, 47-803748Q01, 47-803748K01, 853792T06 |
| Tohatsu / Nissan Part Numbers | 3B2-65021-1, 3B2-65021-0, 3B2650210, 3B2-650210 |
| Johnson / Evinrude Part Numbers | 5040525, 05040525 |
| Sierra Cross Reference | 18-8920 |
| Blades | 6 |
| Material | Neoprene and hardened nylon hub |
| Hub Size | 0.472 in, 12.0 mm |
| Outer Diameter | 1.587 in, 40.3 mm |
| Height | 0.709 in, 18.0 mm |
| Fits | Mercury, Tohatsu and Nissan 4 stroke outboards 6 HP to 9.9 HP |
| Package Contents | 1 x impeller, 1 x housing gasket, 1 x plate gasket, 1 x key |
| Country of Origin | Taiwan |
| Impeller Net Weight | 20 g |
| Net Weight | 30 g including packaging |
| Pack Size | 150 mm x 180 mm x 30 mm |
| Pack Size In Inches | 5.91 in x 7.09 in x 1.18 in |
| Warranty | 3 year |
OEM Cross Reference
| Brand | Part Numbers |
|---|---|
| Mercury Marine | 47-803748-1, 8037481, 47-803748Q01, 47-803748K01, 853792T06 |
| Nissan Tohatsu | 3B2-65021-1, 3B2-65021-1M, 3B2-650211M, 3B2-65021-0, 3B2650210, 3B2-650210 |
| Johnson / Evinrude OMC BRP | 5040525, 05040525 |
| Sierra Marine | 18-8920 |
Compatible Engines
| Brand | Horsepower | Model or Serial Range |
|---|---|---|
| Mercury | 6 HP | 0N027903 through 0N055109, 0N055110 and up |
| Mercury | 8 HP | 0N014717 and up, 0N027903 through 0N055109, 0R042475 and up |
| Mercury | 8 HP 209cc | 0P325500 and up |
| Mercury | 9.8 HP | 0N007788 through 0N055109, 0N055110 and up |
| Mercury | 9.9 HP | 0N260037 and up, 0P325500 and up, 0R042475 and up |
| Mercury | 9.9 HP BigFoot | 0P325500 and up |
| Nissan / Tohatsu | 6 HP | NS6B, M6B |
| Nissan / Tohatsu | 8 HP | NS8B, NSF8A, NSF8A2, NSF8A3 |
| Nissan / Tohatsu | 8 HP | M8B, MFS8A, MFS8A2, MFS8A3, MFS8B |
| Nissan / Tohatsu | 9.8 HP | NS9.8B, NSF9.8A, NSF9.8A2, NSF9.8A3 |
| Nissan / Tohatsu | 9.8 HP | M9.8B, MFS9.8A, MFS9.8A2, MFS9.8A3, MFS9.8B |
What's Included
| Component | Detail | Qty |
|---|---|---|
| Impeller 3B2-65021-1 | 6 blade, neoprene, hardened nylon hub | 1 |
| Housing gasket 161586 / 3B2-65029 | Seals the pump cover joint | 1 |
| Plate gasket 161585 / 3B2-65018 | Seals the wear plate | 1 |
| Drive key 9521811 / 3B2-65022-0 | 3 mm x 11 mm stainless pin | 1 |
| Pump housing and wear plate | Not included, reuse the originals | 0 |
Signs The Pump Kit Needs Fitting
| What You See | What It Means | What To Do |
|---|---|---|
| Tell tale weak or dry at idle | Blades bent or worn | Fit the new kit |
| Motor runs hot after a long run | Pump flow short of demand | Fit the new kit |
| Black rubber in the tell tale | Blade breaking up | Fit the new kit and flush the passages |
| Water in the gear oil | Housing gasket or plate gasket failed | Fit the new kit and reseal the housing |
| Impeller turns but pumps nothing | Drive key missing or rounded | Fit the new kit |
| Two seasons since the last change | Past the service interval | Fit the new kit |
Fitting Notes
| Step | Action |
|---|---|
| 1 | Check the horsepower and serial number against the table above |
| 2 | Drop the lower unit and take the pump housing apart |
| 3 | Note which way the blades were bent before removing the impeller |
| 4 | Take the old impeller off and pick the key out of the shaft slot |
| 5 | Clean both gasket faces and check the wear plate for grooves |
| 6 | Fit the plate gasket, the key and the new impeller |
| 7 | Fit the housing with the blades bent in the running direction and the cover gasket in place |
| 8 | Refit the lower unit, run on muffs and check the tell tale is strong |
Condition & Warranty
| Item | Detail |
|---|---|
| Condition | New / New with tags |
| Warranty | 3 year |
| Packaging | Sealed retail packaging |
Before You Buy
- Fits Mercury 6, 8, 9.8 and 9.9 HP four stroke outboards
- Fits Nissan and Tohatsu 6, 8 and 9.8 HP four stroke outboards
- Replaces Mercury 47-803748-1 and Tohatsu 3B2-65021-1
- Crosses to Sierra 18-8920 and OMC BRP 5040525
- 6 blade impeller in neoprene with a hardened nylon hub
- Outer diameter 1.587 in, 40.3 mm
- Kit includes the impeller, two gaskets and the drive key
- 30 g with packaging, box 150 mm x 180 mm x 30 mm
- Check the serial number before ordering
- 30-Day Easy Returns
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