Mercury 8.1S Horizon, Product Applications Manual

Page: 75 / 163

Exhaust System
Page 6A-6 90-863758060 AUGUST 2006
The interactive nature of these factors makes it difficult to predict which exhaust system
designs will be susceptible to the tuning effect. To address this situation, Mercury
MerCruiser has developed exhaust resonators that are installed aft of the exhaust elbow
outlets. The resonators help to break up the reverse pulsations yet do not affect the engine
performance. In some cases, a performance increase is actually realized by using the
resonators.
Mercury MerCruiser recommends the use of the resonators on all models that have water
present after water intrusion testing has been completed, and the exhaust system has been
confirmed to meet all specifications, as outlined in this manual. Resonators are typically
more beneficial for large engines, but can be used on other models as well. The kit is
available through Mercury Precision Parts and Accessories.
Resonators are installed as shown. Because of the critical nature of the placement of the
resonator, Mercury MerCruiser will free license this technology to allow the resonator to be
built into your muffler. Contact your product application engineer for details.
The exhaust resonator is positioned with the inside flat surface at the preferred distance
of 43 cm (17 in.) from the front edge of the exhaust hose. The 43 cm (17 in.) dimension
can be reduced, if necessary, to a minimum of 33 cm (13 in.). This dimension must be the
same on both exhaust outlets. The boat builders must test to find the optimum resonator
placement for each type of exhaust system.
IMPORTANT: Complete the water intrusion test to ensure that the resonators are installed
properly.
d
e
b
f
a
c
g
20454
a - Exhaust resonator
b - Exhaust hose
c - Dimension to inside flat surface of
resonator 33–43 cm (13–17 in.)
d - No less than 51 mm (2 in.)
between resonator and exhaust
outlet or closest fitting
e - Hose clamp positioned around
center of resonator for retention
f - Exhaust outlet
g - Exhaust elbow