The Water Pump Inlet Guide Tube (Sleeve) is a small but essential component in the cooling systems of a wide range of Mercury, Mariner, Force, and MerCruiser engines.
 
This white plastic sleeve (29804), which is installed into the water pump housing, serves a simple but critical function: guiding the copper water tube into proper alignment with the water pump during assembly.
 
When correctly installed, it ensures uninterrupted water flow from the pump to the engine, which is essential for regulating engine temperature.
 
Over time, this part is subject to wear. Because it is made of heat-sensitive plastic, it can melt, deform, or crack after extended exposure to engine heat, especially in cases where the engine has overheated or the cooling system has been compromised.
 
A damaged or missing guide sleeve can allow the water tube to misalign with the pump, potentially leading to restricted water flow, overheating, or premature failure of the impeller or pump housing. For this reason, it’s considered good practice to inspect and replace the sleeve anytime the water pump is serviced.
 
This guide tube sleeve is commonly associated with Mercury part numbers 23-29804, 29804T, 23-52928, and 23-29804T, and it appears across a broad spectrum of engines.
 
Among the smaller 4-stroke outboards, it is used in the 9.9 HP (323 cc), 13.5 HP, 15 HP, and 15 Marathon XD models. It’s also found in the 20 HP and 25 HP 2-cylinder outboards, including variants like the 20 Jet, 25 Marathon, and the Super 15. For jet drive applications, compatibility extends to models such as the 110 Jet (2.5L) and the 140 Jet.
 
In mid- and high-performance outboard categories, the sleeve supports a range of legacy and modern engines, including the Magnum III, V-115 DFI (2.5L), V-135 and V-135 DFI (2.5L), as well as international models like the V-140.
 
The V-150, V-150 EFI, and V-150 DFI (2.5L) also use this part, along with the V-175 EFI and V-175 DFI (2.5L). Larger engines such as the V-200, V-200 EFI, and the V-200 EFI (2.5L) rely on it for proper cooling system alignment.
 
The sleeve is also found in many high-output and performance models like the XR-6 (serial numbers 0G960500 through 1B226999), the 200 EFI Pro Max, Super Magnum, and the 200XS DFI (2.5L).
 
Higher-horsepower configurations such as the 150 Pro XS (2.5L) (serial numbers 1B690542 & up) and 175 Pro XS (2.5L) (serial numbers 1B516339 & up) also include this part in their cooling assemblies.
 
In addition to outboards, this sleeve is used in MerCruiser sterndrive systems, including the R/MR/Alpha One sterndrive and transom assembly configurations. In these systems, just as with outboards, the sleeve ensures that water is routed properly from the pickup tube through the pump and into the engine's cooling system.
 
Because of its role and vulnerability to heat degradation, the Quicksilver water tube alignment sleeve should be inspected during any water pump or impeller replacement. If any signs of warping, melting, or cracking are found, it should be replaced immediately to maintain proper function.
 
Using a damaged sleeve may not prevent immediate engine operation, but it can compromise cooling efficiency and eventually lead to significant engine damage.
 
For long-term reliability and proper fitment, replacing this guide sleeve with an OEM Mercury Marine part is recommended. Ensuring the correct part is used for your specific engine model helps maintain consistent cooling system performance and extends the service life of critical components.