Water Pump Base 46-44292A3 for MerCruiser Alpha One Gen 1 MR Sterndrive 18-3420
Water Pump Base 46-44292A3 for MerCruiser Alpha One Gen 1 MR Sterndrive 18-3420
Product Overview
Water pump base, a direct replacement part for MerCruiser MR and Alpha One Generation I sterndrives built from 1972 to 1990. It replaces MerCruiser 46-44292A3, 46-44292Q03 and 46-44292T1, and crosses to GLM 12320, Mallory 9-43308 and Sierra 18-3420. The base comes in a 150 mm x 100 mm x 40 mm box and weighs 155 g with packaging.
The base is the lower half of the water pump housing. The impeller runs against it, so its bore and sealing face set how much water the pump moves. Once the bore is scored or the seal face is worn, a new impeller alone will not restore flow.
The casting is the original pattern, with the same bolt spacing and the same water passage as the Mercury part. It takes the standard impeller and wear plate for these drives, so it can be fitted to a pump you already have apart rather than ordering a whole housing.
Fitment runs across two groups on our eBay listings: the MerCruiser MR sterndrive from 1972 to 1982 and the Alpha One Generation I from 1983 to 1990, plus the Mercury, Mariner and Force L4, L6 and V6 two stroke outboards from 65-225 HP. Check the drive model and the year before ordering.
Specifications
| Specification | Detail |
|---|---|
| Condition | New / New with tags |
| Type | Water pump base, lower housing |
| MerCruiser Part Numbers | 46-44292A3, 46-44292Q03, 46-44292T1 |
| GLM Cross Reference | 12320 |
| Mallory Cross Reference | 9-43308 |
| Sierra Cross Reference | 18-3420 |
| Fits | MerCruiser MR and Alpha One Gen I sterndrives |
| Fits Years | 1972 to 1990 |
| Also Listed For | Mercury, Mariner and Force L4, L6 and V6 two strokes, 65 HP to 225 HP |
| Material | Marine grade cast alloy |
| Package Contents | 1 x water pump base |
| Net Weight | 155 g including packaging |
| Pack Size | 150 mm x 100 mm x 40 mm |
| Pack Size In Inches | 5.91 in x 3.94 in x 1.57 in |
| Warranty | 3 year |
OEM Cross Reference
| Brand | Part Numbers |
|---|---|
| MerCruiser | 46-44292A3, 46-44292Q03, 46-44292T1 |
| Mercury Marine | 46-44292A3, 46-44292Q03, 46-44292T1 |
| GLM | 12320 |
| Mallory | 9-43308 |
| Sierra | 18-3420 |
Compatible Engines
| Brand | Model | Years | Notes |
|---|---|---|---|
| MerCruiser | MR sterndrive | 1972 to 1982 | Generation I pump |
| MerCruiser | Alpha One Generation I sterndrive | 1983 to 1990 | Generation I pump |
| Mercury | L4, L6 and V6 two stroke | 65 HP to 225 HP | As listed on our outboard fitment |
| Mariner | L4, L6 and V6 two stroke | 65 HP to 225 HP | As listed on our outboard fitment |
| Force | L4, L6 and V6 two stroke | 65 HP to 225 HP | As listed on our outboard fitment |
What's Included
| Component | Detail | Qty |
|---|---|---|
| Water pump base | 46-44292A3, complete lower housing | 1 |
| Impeller | Not included, sold separately | 0 |
| Wear plate | Not included, sold separately | 0 |
| Gaskets | Not included, sold separately | 0 |
Signs The Base Needs Replacing
| What You See | What It Means | What To Do |
|---|---|---|
| New impeller but still overheating | Base bore worn, blades cannot seal | Fit the new base |
| Deep grooves in the bore | Sand or grit run through the pump | Fit the new base |
| White corrosion on the sealing face | Salt water attack on the casting | Fit the new base |
| Water in the gear oil | Seal face gone, water past the pump | Fit the new base and reseal |
| Tell tale weak at idle | Pump clearances out of spec | Fit the new base and impeller |
| Base cracked around a bolt hole | Over tightened or frozen bolt | Fit the new base |
Fitting Notes
| Step | Action |
|---|---|
| 1 | Read the drive model and year and check the table above |
| 2 | Put the drive in gear, remove the propeller and split the lower unit |
| 3 | Take the pump housing and impeller off and note the blade direction |
| 4 | Remove the base and clean the mating face on the gear housing |
| 5 | Check the new base sits flat with no gap under it |
| 6 | Fit the new base, then the wear plate and gasket, then the impeller |
| 7 | Refit the housing and tighten the bolts evenly in a cross pattern |
| 8 | Turn the driveshaft by hand to check the impeller turns freely |
| 9 | Run the engine on muffs and confirm a strong tell tale before you launch |
Condition & Warranty
| Item | Detail |
|---|---|
| Condition | New / New with tags |
| Warranty | 3 year |
| Packaging | Sealed retail packaging |
Before You Buy
- Fits MerCruiser MR sterndrives from 1972 to 1982
- Fits MerCruiser Alpha One Generation I sterndrives from 1983 to 1990
- Also listed for Mercury, Mariner and Force L4, L6 and V6 two strokes from 65 HP to 225 HP
- Replaces MerCruiser 46-44292A3, 46-44292Q03 and 46-44292T1
- Crosses to GLM 12320, Mallory 9-43308 and Sierra 18-3420
- Marine grade cast alloy, original pattern bore and bolt spacing
- 155 g with packaging, box 150 mm x 100 mm x 40 mm
- 30-Day Easy Returns
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Boat Owners' Review
Before You Buy
Frequently Asked Questions
What is your refund policy?
We offer a 14-day hassle-free return on all products. Items must be unused and in original packaging. Every XRmarine part is also covered by our 1-year warranty against manufacturing defects. If something is not right, email us at info@xrmarineparts.com — replacement or full refund, your choice.
See our full Refund Policy for complete details.
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