Mercury MERCRUISER, Service Manual, Page: 415 / 566

Air‑Actuated Drain System
Air Manifold and Air Pump—Exploded View
1
3
2
4
5
6
7
8
9
10
56844
Ref. No. Qty. Description
Torque
Nm lb‑in. lb‑ft
1 1 Air pump
2 2 Screw (for remote mounting)
3 1 Air pump bracket
4 2 M5 screw 2.3 20.3 –
5 2 Washer
6 1 Air manifold assembly
7 1 Service point cap
8 2 Gray air hose
9 2 Black air hose
10 1 Nylon clamp
General Information
The air‑actuated drain system uses compressed air to move a piston that pulls a plug out of a drain port or moves a drain tube
to expose a hole to a water passage allowing water to drain into the engine compartment. All of the drain locations are
arranged to allow any debris to be continually flushed away from the drains during normal engine operation. A feedback
mechanism provides positive indication of proper piston movement. When each piston moves far enough in its cylinder, a port
is uncovered that allows compressed air to flow back to the air manifold and cause the green indicator to extend. The drains
are closed by opening the manual release valve that releases the compressed air from the system. The manual release valve
also functions as an automatic pressure relief valve that opens at approximately 482.7 kPa (70 psi), thereby protecting the
compressed air circuit from damage due to excess pressure.
Testing
!
CAUTION
Water can enter the bilge when the drain system is open, damaging the engine or causing the boat to sink. Remove the boat
from the water or close the seacock, disconnect and plug the seawater inlet hose, and ensure the bilge pump is operational
before draining. Do not operate the engine with the drain system open.
!
CAUTION
Removing the snap ring from the top of the air‑actuated drain valve can allow the components to come apart forcefully,
resulting in injury or product damage. Do not try to repair the valve or remove the snap ring.
All Models
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 6A-11