Technical data

It is essential not to hang too much weight in the form of exhaust system components rigidly
from the engine manifold. Generally, it is permissible to directly connect a pipe nipple and a water
jacketed exhaust elbow, which two components weigh about 8 pounds (4 kg). If there are more
components to be rigidly connected to each other than will weigh 8 pounds, then a flexible exhaust
section must be installed between manifold outlet and the exhaust system.
The exhaust system must be supported or suspended independently of the engine manifo+d,
usually using simple metal hangers secured to the overhead.:
All dry portions of the exhaust system should be wrapped in suitable insulation material to keep
surface temperatures as low as possible.
Many installations use flexible rubber exhaust hose for the water cooled section of the exhaust
line because of the ease of installation and flexibility. Provide adequate support for the rubber hose to
prevent sagging, bending and formation of water pockets,
Always arrange the rubber hose section so that water cannot possibly flow back into the engine.
Also make sure that entering sea water cannot spray directly against the inside of the exhaust piping.
Otherwise, excessive erosion will occur.
MEASURING EXHAUST GAS BACK PRESSURE
Back pressure must be measured on a straight section of the exhaust line and as near as possible
to the engine exhaust manifold. The engine should be run at maximum load during the measurement
period. Set-up should be as shown below.
1. For normally asperated engines:
Pressure Test Mercury Test Water Column
1-1/2" Max PSI 3" Mercury = 39"
2. For turbo-charged engines:
Pressure Test Mercury Test Water Column
0.75 Max PSI 1-1/2" Mercury = 19-1/2"