Combination exhaust manifold and exhaust elbow for marine propulsion system

A combination exhaust manifold and exhaust elbow for an internal combustion engine includes an exhaust cavity for receiving exhaust from the engine, an exhaust passage leading from the exhaust cavity, and an exhaust discharge outlet. A first water jacket is provided around the exhaust cavity and a second water jacket is provided around the exhaust discharge passage. A dam is provided between the first and second water jackets, having a passage therein for allowing fluid communication between the first and second water jackets. A warm water inlet is provided in the first water jacket around the exhaust cavity for receiving cooling water which has been warmed by the engine, and which flow is controlled by a temperature sensitive thermostat. A cold water inlet is provided adjacent the discharge exhaust passage. The cold water inlet is disposed either upstream or downstream of the dam adjacent the exhaust passage, and allows cold bypass water to be discharged without the necessity of the cold water flowing through the entire assembly, so as to prevent moisture from condensing out of the exhaust in the exhaust cavity.

DETAILED DESCRIPTION OF THE PRIOR ART 
With reference to FIG. 1, a prior art system for discharging exhaust and 
cooling water includes an exhaust manifold 201 to which an exhaust elbow 
203 is mounted. Manifold 201 includes an exhaust collecting cavity 205 
which receives engine exhaust through a plurality of inlets 207, 209, 211. 
An exhaust discharge outlet 213 is provided at the upper end of manifold 
201, so that exhaust is discharged into an exhaust passage 215 provided in 
exhaust elbow 203 for ultimate discharge through discharge end 217 of 
exhaust elbow 203. 
Manifold 201 is water jacketed, including water passages as shown at 219, 
221, 223. An inlet 225 is provided in the bottom wall of manifold 201 for 
introducing water into the manifold water jacket at certain conditions, as 
will be explained. Manifold water jacket outlets, such as shown at 227, 
228, are provided at the upper end of manifold 201 for discharging water 
therefrom. 
The details of construction of exhaust elbow 203 are set forth in U.S. Pat. 
No. 4,573,318 to Entringer et al, the disclosure of which is hereby 
incorporated by reference. For purposes of explanation, an overview of the 
construction of exhaust elbow 203 is provided. 
As noted previously, exhaust elbow 203 includes an exhaust passage 215, 
which has a substantially vertical inlet portion which communicates 
through a bend to a substantially horizontal outlet portion. 
Exhaust elbow 203 includes a water jacket 229, which has inlets in 
communication with manifold water jacket outlets 227, 228 for allowing 
water flow upwardly from manifold 201 through exhaust elbow 203 for 
ultimate discharge through an outlet 231 provided at the leftward end of 
water jacket 229. 
An inlet 233 is provided in the rightward sidewall of water jacket 229 for 
introducing cooling water into the water jacket around exhaust passage 
215. Inlet 233 communicates with a central channel section 235, from which 
water is directed by means of a pair of sidewalls, one of which is shown 
at 237, over the top of exhaust passage 215. A sidewall similar to that 
shown at 237 is spaced from sidewall 237 so that a restricted water 
passage is provided therebetween. 
Cooling water is constantly supplied to exhaust elbow inlet 233 both at 
start-up and after the engine cooling water is sufficiently warmed to open 
the thermostat. Warmed cooling water is introduced into inlet 225 in the 
bottom of exhaust manifold 201 when the thermostat is open. 
At start-up and prior to opening of the thermostat, the only flow occurs 
through exhaust elbow inlet 233. In this situation, water present in the 
water jacket around exhaust manifold 201 remains in place, and water 
introduced through exhaust elbow inlet 233 flows upwardly through central 
channel section 235 and through the restricted area provided between the 
sidewalls atop exhaust passage 215, one of which is shown at 237. Such 
water then continues flowing over exhaust passage 215 and is ultimately 
discharged from outlet 231. 
After water is sufficiently warmed to open the thermostat, warmed water 
introduced through exhaust manifold inlet 225 flows upwardly through water 
passages 219, 221 and 223 and is discharged into exhaust elbow 203 through 
outlets 227, 228. This water then mixes with water introduced through 
exhaust elbow inlet 233 for ultimate discharge through outlet 231. 
With reference to FIG. 2, a one-piece prior art exhaust discharge assembly 
245 includes a manifold portion 247 and an exhaust elbow portion 249. An 
exhaust cavity 251 is provided in manifold portion 247 for receiving 
engine exhaust through exhaust inlet passages 253. A series of apertures 
255 are formed in and through the lower portion of manifold portion 247 
for receiving bolts to mount assembly 245 to an engine. 
An upper exhaust passage 257 is provided in the upper portion of manifold 
portion 249 for discharging exhaust therefrom into an exhaust passage 259 
formed in elbow portion 249. Exhaust passage 259 leads to an exhaust 
discharge outlet 261. 
A cooling water jacket is provided around manifold portion 247 for cooling 
exhaust contained within exhaust cavity 251 prior to discharge of such 
exhaust. The water jacket around exhaust cavity 251 includes a bottom 
portion 263 and front and rear portions 267, 265, respectively. With 
reference to FIG. 3, the water jacket around exhaust cavity 251 further 
includes right and left side portions 269, 271, respectively. An upper 
portion 273 and a lower portion 275 are provided around upper exhaust 
passage 257. 
A cooling water jacket is also provided around elbow portion 249, including 
top and bottom portions 277, 279, respectively. Side portions (not shown) 
provide circulation of cooling water around the sides of elbow portion 
249. A water discharge outlet 281 is provided at the lower end of the 
water jacket downstream of exhaust outlet 261. A mixing tube or other 
satisfactory device (not shown) is mounted to the lower end of exhaust 
elbow portion 249 for discharging mixed exhaust and cooling water. 
A dam 283 substantially separates the cooling water jackets provided around 
manifold portion 247 and elbow portion 249. An upper passage 285 is formed 
in the upper portion of dam 283. 
An inlet 289 is provided at the lower front area of manifold portion 247 
for introducing water from the engine cooling system into the manifold 
water jacket. A drain opening 291 is provided in the lower wall of 
manifold portion 247, and is in communication with bottom water jacket 
portion 263. Depending upon the application in which assembly 245 is used, 
either opening 291 or inlet 289 is employed for introducing water into the 
manifold water jacket. For purposes of further explanation, it will be 
assumed that inlet 289 is utilized for introducing water into the manifold 
water jacket, and opening 291 is plugged. 
In the prior art system in which assembly 245 is utilized, water is always 
supplied to inlet 289 for circulation through the manifold water jacket. 
The circulated water includes water discharged from the engine cooling 
system, as well as any overflow intake water which bypasses the engine 
cooling system. The excess water is mixed with discharged engine cooling 
water prior to introduction through inlet 289. With this arrangement, 
prior to engine warm-up, cold water is introduced through inlet 289, which 
results in moisture condensing out of exhaust contained within exhaust 
cavity 251. Additionally, with the structure as shown and described, a hot 
spot is formed at the lower right area of manifold portion 247. The hot 
spot is a result of inadequate water circulation in this area, in that 
water flow through the manifold water jacket tends to move in a direction 
from the lower left to the upper right, resulting in inadequate 
circulation through the lower right portion of the manifold water jacket. 
With reference to FIG. 3, in certain portions of bottom water jacket 
portion 263, a wall 291 having an opening 293 is formed. With the 
described construction, a water passage 295 is provided to the right of 
wall 292, and the area 297 to left of wall 292 is obstructed. It has been 
found that this arrangement provides unsatisfactory water flow through 
bottom water jacket portion 263. 
DETAILED DESCRIPTION OF THE INVENTION 
With references to FIG. 4, an exhaust discharge assembly 10 is connected by 
means of bolts 11 to an internal combustion engine, schematically 
presented at 12. The water circulation system for engine 12 is shown 
schematically, and includes an inlet line 14 connected to a fitting 16. A 
line 18 leads from fitting 16 to a circulating water pump 20. Pump 20 is 
adapted to pump cooling water into one or more engine cooling water 
inlets, schematically shown at 22. The cooling water then flows through 
the cooling system provided in engine 12 as is well known, and exits from 
engine 12 via one or more cooling water outlets, shown schematically at 
24. The cooling water exiting engine 12 through outlet 24 flows to a 
temperature flow control means, such as a thermostatic valve 26. A 
connection 27 is provided between thermostatic valve 26 and fitting 16 so 
as to allow water flow therebetween. Thermostatic valve 26 is also 
connected via a line 28 to a warm water inlet 30 provided in the lower 
portion of exhaust discharge assembly 10. A line 32 connects fitting 16 to 
a cold water inlet 34 provided in the upper portion of exhaust discharge 
assembly 10. Thermostatic valve 26 may be provided with a small bypass to 
allow limited flow when in its closed condition to stabilize temperature 
within the engine cooling system. 
During start-up and low speed operation, cooling water exiting engine 12 
through outlet 24 is not sufficiently warmed by engine 12 to cause 
thermostatic valve 26 open, thus providing no significant flow in line 28 
leading to warm water inlet 30. Such unwarmed water then either reenters 
the engine cooling system via line 18 or is routed via line 32 to cold 
water inlet 34 provided on exhaust discharge assembly 10. After warm-up, 
engine cooling water exiting engine 12 via outlet 24 is sufficiently 
warmed to cause thermostatic valve 26 to open. Such warmed water is then 
routed via line 28 to warm water inlet 30 provided on exhaust discharge 
assembly 10. Excess warmed water which does not pass into line 28 is 
routed via connection 27 to fitting 16 and mixed with cold incoming water 
for recirculation through the engine cooling system. 
Excess cooling water flowing into fitting 16 via line 14 which does not 
pass into pump 20 via line 18 is bypassed through line 32 to cold water 
inlet 34 provided on exhaust discharge assembly 10. 
With reference to FIG. 5, exhaust discharge assembly 10 includes a manifold 
portion 36 and an exhaust elbow portion 38. An exhaust cavity 40 is 
provided in manifold portion 36 for receiving exhaust from engine 12. 
Exhaust inlet passages 42 are provided in the lower portion of manifold 
portion 36 for allowing exhaust to pass from engine 12 to exhaust cavity 
40. A series of apertures 44 are formed in and through the lower portion 
of manifold portion 36 for receiving bolts 11 therethrough for mounting 
exhaust discharge assembly 10 to engine 12. 
An exhaust passage 46 is provided in the upper portion of manifold portion 
36 for discharging exhaust therefrom into an exhaust passage 48 formed in 
elbow portion 38. Exhaust passage 48 leads to an exhaust discharge outlet 
50. 
As best shown in FIGS. 5 and 7, a cooling water jacket is provided around 
manifold portion 36 for cooling exhaust contained within exhaust cavity 40 
prior to discharge of such exhaust. The water jacket around exhaust cavity 
40 includes an inlet portion 51, a front portion 52, a rear portion 54, a 
ducting portion 56, and right and left side portions 57 and 58, 
respectively. An upper portion 59 and a lower portion 60 are provided 
around exhaust passage 46. A bleed passage 61 provides limited 
communication between water jacket front portion 52 and inlet portion 51. 
A cooling water jacket is also provided around elbow portion 38, including 
top and bottom portion 62 and 64, respectively. Side portions (not shown) 
provide circulation of cooling water around the sides of elbow portion 38. 
A circumferential water discharge outlet 65 is provided at the lower ends 
of the water jacket around the exterior of exhaust passage 48. Water 
discharge outlet 65 is provided upstream of exhaust discharge outlet 50. 
The lower end of elbow portion 38 is adapted to receive a mixing tube or 
other such fitting for discharging mixed exhaust and cooling water from 
the boat. The placement of exhaust outlet 50 below water outlet 65 
prevents cooling water from creeping upwardly through exhaust passage 48 
and into exhaust cavity 40. Such ingestion of water can cause fouling and 
corrosion of engine 12 and of the interior surfaces of exhaust cavity 40. 
A dam 66 substantially separates the cooling water jackets provided around 
manifold portion 36 and elbow portion 38. A passage 68 is formed in the 
upper portion of dam 66, providing fluid communication between upper 
portion 59 around exhaust passage 46 and top portion 62 around elbow 
portion 38. 
As shown in FIGS. 5-7, a warm water inlet 30 introduces warm water into 
inlet portion 51 in the water jacket around manifold portion 36. Cold 
water inlet 34 is disposed adjacent dam 66, and introduces cold water into 
top portion 62 in the water jacket around exhaust passage 46. 
A drain opening 70 is provided in bottom portion 56 in the water jacket 
around manifold portion 36. Drain opening 70 functions as a means for 
draining water from exhaust discharge assembly 10. In normal operation, 
drain opening 70 is closed off by means of a cap 72 clamped onto drain 
opening 70 by a clamp 74. However, drain opening 70 may be used as a warm 
water inlet in lieu of warm water inlet 30 in applications where inlet 30 
is inaccessible. In this situation, line 28 would be connected to drain 
opening 70 and inlet opening 30 would be capped. 
In operation, exhaust discharge assembly 10 functions as follows. On start 
up and during low speed operation, cooling water flowing through engine 12 
is not sufficiently warmed by engine 12 to cause thermostatic valve 26 to 
open. The cooling water is then recirculated through engine 12 or is 
bypassed via line 32 to cold water inlet 34. Such unwarmed water entering 
cold water inlet 34 passes into top and bottom portions 62 and 64, 
respectively, in the water jacket around elbow portion 38 and is 
discharged therefrom via water outlet 65. In this situation the water flow 
is relatively low, since the flow of engine cooling water supplied by pump 
20 is proportional to engine speed. 
During start-up and low speed operation, there is little if any circulation 
in the water jacket around exhaust cavity 40. Thus, cooling water 
contained therein during such operation will be sufficiently warmed by 
exhaust flowing through cavity 40 so as to prevent condensation. 
After warm-up, the engine cooling water is sufficiently warmed by engine 12 
to cause thermostatic valve 26 to open and warm water to flow via line 28 
to warm water inlet 30. Such warmed water then flows downwardly through 
inlet portion 51 by a wall 51a and into ducting portion 56, and then 
passes through a series of orifices 80, 82, 84 and 86 into the water 
jacket around exhaust cavity 40 to cool exhaust contained therein prior to 
its discharge via passage 46. This arrangement allows for a substantially 
even flow of circulating water to the walls of exhaust cavity 40. A small 
amount of such water passes directly from inlet portion 51 to water jacket 
front portion 52 through bleed opening 61. Opening 61 additionally allows 
any air which may enter through inlet portion 51 to escape upwards. 
Trapped air within the water jacket is known to create hot spots. The 
water circulates through the water jacket around exhaust cavity 40 and 
over dam 66 via passage 68 and into the water jacket around exhaust 
passage 46 and 48, where the warmed water mixes with unwarmed bypass water 
passing through inlet 34. The mixed water is then discharged through water 
discharge outlet 65. 
The above-described operation is substantially similar in the event inlet 
30 is capped and drain opening 70 is employed as the water inlet. In this 
situation, water flowing through opening 70 circulates through ducting 
portion 56 in the same manner as described above. Bleed opening 61 allows 
a limited amount of water to circulate through water jacket portion 51 and 
into front water jacket portion 52 for providing an even supply of 
circulating water to the walls of exhaust cavity 40 adjacent lower left 
exhaust inlet 42. 
The circulation of relatively warm cooling water in the water jacket around 
exhaust cavity 40 allows the walls of cavity 40 to remain at a 
sufficiently high temperature that moisture does not condense out of 
exhaust passing through cavity 40. However, the temperature of the water 
circulating in the water jacket around exhaust cavity 40 is sufficiently 
low to cool the exhaust prior to its discharge. 
Another embodiment of exhaust discharge assembly 10 is shown in FIG. 9. 
Inlet 34 is located upstream of dam 66 and introduces cold water into 
upper portion 59 and 62 of the water jackets around exhaust cavity 40 and 
exhaust passage 46, respectively, in such a manner as to minimize the 
amount of turbulence introduced into the relatively quiescent water within 
the exhaust cavity water jacket. During start-up and low speed operation, 
there is again substantially no flow of warm water into warm water inlet 
30 due to the action of thermostatic valve 26. The unwarmed water 
bypassing the engine cooling system via line 32 and entering cold water 
inlet 34 first enters or flows into portions 59-60 in the water jacket 
around exhaust cavity 40. This water is then sufficiently warmed by 
exhaust passing through exhaust cavity 40 to prevent moisture from 
condensing out of such exhaust. During continued low speed or cold 
operation, unwarmed water continues to be fed into cold water inlet 34, 
flowing through upper portion 59 and passage 68 into portions 62 and 64 in 
the water jacket around elbow portion 38 for discharge via discharge 
outlet 65. The water flow during such low speed or start-up operation is 
relatively low, and such low flow of unwarmed water through inlet 34, 
portion 59 and through passage 68 causes a minimal amount of turbulence so 
as not to disturb the warmed water contained within portions 52, 54, 56, 
57, 58 and 60 in the water jacket around exhaust cavity 40 thereby 
preventing excessive cooling of the exhaust gases and subsequent moisture 
condensation. After warm-up, warm water is introduced into warm water 
inlet 30 and passes through the water jacket around exhaust cavity 40 as 
described previously. Cold bypass water flowing through line 32 and cold 
water inlet 34 is mixed with the warmed engine water prior to its passage 
through passage 68 and discharge via water discharge outlet 65. With the 
embodiment of FIG. 9, there is always flow of water through passage 68 and 
any debris contained within the cooling water is continually removed from 
passage 68. 
Various alternatives and modifications are contemplated as being within the 
scope of the following claims particularly pointing out and distinctly 
claiming the invention.