Double Feed Outboard Flush Muffs Rectangular Cups Garden Hose MMS-3440A
mms-3440a
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Double-Feed Rectangular Outboard Flush Muffs
Twin-side water feed | standard garden-hose connection
A twin-feed flushing attachment with rectangular rubber cups designed to deliver fresh water to both sides of a compatible outboard lower-unit intake.
Key Features
- Water supplied to both cups
- Rectangular rubber sealing cups
- Fits a standard garden-hose connection
- For compatible side-intake lower units
- Aftermarket service accessory
Technical Specs
| Feed type | Double / both sides |
| Cup shape | Rectangular |
| Water connection | Standard garden hose |
| Application | Compatible outboard lower-leg side intakes |
| 4Boats SKU | mms-3440a |
Compatibility / Fitment Guide
These muffs are selected by intake position, cup size and water-supply connection — not by horsepower or brand alone.
| Compatible intake layout | Lower units with opposed side intake slots that fit completely inside the rectangular cups. |
| Cup fit | Both cups must sit flat and fully cover every side intake slot. They must remain sealed when water pressure is applied; damaged, painted or unusually shaped gearcases may not seal. |
| Check for extra intakes | Not suitable by itself for nose-cone, low-water-pickup, under-cavitation-plate or other uncovered intake designs. Follow the engine manual for taping/closing additional inlets or using the specified adaptor. |
| Water supply | Connect to a standard garden hose and open the tap enough to keep both cups sealed and supplied. Confirm water reaches both sides before any permitted engine start. |
| Engine operation | Do not start the engine merely because muffs are fitted. Run only if the manufacturer’s flushing procedure explicitly permits it, with the gearcase vertical, gearbox in neutral, propeller area clear and a strong continuous water supply. |
| Not for | Sterndrives or inboards unless their manual specifically permits this muff arrangement; engines with a dedicated flush-port-only procedure; frozen/damaged cups; unattended running. |
Part Number Cross Reference
| Flusher style | Double-feed rectangular-cup muffs |
| Water connection | Standard garden hose |
| 4Boats SKU | mms-3440a |
No OEM engine part number is claimed. The engine owner’s manual and the physical water-intake layout determine compatibility.
Frequently Asked Questions
Will these fit every outboard?
No. Both cups must cover the complete intake pattern and the engine manual must allow muff flushing.
Can I run the engine while flushing?
Only where the engine maker’s procedure expressly allows it. Never run without visible cooling-water supply and never leave the engine unattended.
Should the propeller be removed?
For workshop running, removing the propeller is the safest approach where the manual and service procedure allow; otherwise keep the area completely clear and ensure neutral is positively selected.
Why is no tell-tale visible?
Shut down immediately. Check water pressure, cup seal, blocked tell-tale and the model-specific procedure before trying again.
Allow the engine to cool, keep people clear of moving parts and hot exhaust, and never rely on muffs that do not seal positively over all required intakes.
For the products under £150 the shipping is £6.99.
Free delivery for most items over £150.
