Check For Water Intrusion - Mercury MerCruiser Product Applications Manual

Exhaust System
Description
Drill and 3/8 in. drill bits or bit that match fittings
Service Tachometer
Schraeder valve, 2 required
Brass 1/8 in. NPT male adapter fitting ‑ 2 required
Pressure gauge accurate to 7 kPa (1 psi)
3. Set the pressure gauge to zero before connecting it to the engine.
4. While underway, operate the engine at 1000, 2000, 3000, 4000, and WOT RPM
respectively. Record back pressure at each setting.
5. Repeat steps for the second cylinder bank and remaining engines on multiple engine
applications.
6. Replace exhaust hoses.
If pressure is within specification, changes must be made to the system to reduce the
pressure.

Check for Water Intrusion

IMPORTANT: A check for water intrusion must be performed on all new applications with
through‑transom or through‑hull exhaust.
Select and perform one of the two methods to check for water in the exhaust manifolds.
The exhaust elbow removal method is the simplest and least time‑consuming method
to check for water in the exhaust manifolds. With this method, however, it is difficult to
accurately determine the amount of water in the manifolds.
The exhaust manifold tap method provides a more accurate means to measure the
water, but requires that a hole be drilled in each manifold. The manifolds must be replaced
after performing this check, so the procedure is best performed by Mercury MerCruiser's
product applications engineer or where repeated testing will be performed at your facility.
IMPORTANT: If there is no water in one manifold, do not assume that there is not water
in the other manifold. Check each manifold.
PREPARATION
Consider hose lengths and angle, exhaust elbow height to the water line, waterlift muffler
exhaust outlet angles, water lift muffler water height, idle relief angles, exhaust collector
angles, air temperature, water temperature, and humidity when performing these test.
EXTENDED IDLE TEST
1. Operate the engine until it is at normal operating temperature [73°C (160 °F)].
2. Place the remote control in NEUTRAL. Increase the engine speed to 3000 RPM for 1
minute.
3. Bring the engine back to idle SLOWLY after 1 minute.
4. Shut the engine OFF.
5. Restart the engine and operate at idle speed for 15 minutes.
6. Shut the engine OFF.
7. Check for water
IMPORTANT: If this test is repeated, ensure the engine is at operating temperature and
that the 3000 RPM step is repeated to clear the manifolds of water.
CHECKING BY EXHAUST ELBOW REMOVAL METHOD
NOTE: This test is easier on seawater cooled engines but results are applicable to closed
cooled engines also.
Page 6A-26
Part Number
Obtain locally
Obtain locally
22‑860226
22‑808002
Obtain locally
90-863758060 AUGUST 2006