SEAWATER AND EXHAUST SYSTEM IN AN ENGINE INSTALLATION IN A BOAT

Abstract: Seawater and exhaust system in a marine engine installation, comprising an outlet conduit (12) from a water heat exchanger (11) to the engine exhaust pipe bend (15). The outlet conduit extends from the heat exchanger upwards to a point (21) above the waterline and from there down to the exhaust pipe bend. The downwardly directed conduit section (12b) has such a large flowthrough area relative to the waterflow that air and exhaust can easily pass from the exhaust system up to the highest point when the engine is shut off.

Description: Seawater and exhaust system in an engine installation in a boat The present invention relates to a seawater and exhaust system in a marine engme installation, comprising a water pump, a suction conduit connected between the water pump and the water inlet, a pressure conduit connected between the water pump and an inlet to a heat exchanger, and an outlet conduit which is connected between an outlet from the heat exchanger and an inlet to an exhaust conduit lying completely or partially beneath the waterline of the boat. In smaller marine engine installations, the cooling water m the form of seawater is taken m through a bottom port, passes through the water pump and the heat ex¬ changer and is mixed with exhaust in a water-jacketed exhaust pipe bend. The cool¬ ing water then flows together with the exhaust via a muffler out through a hull port In those cases when the seawater level is level with or above the exhaust pipe bend, there is a πsk that water will penetrate into the suction line of the pipe, pass the pump, the heat exchanger and the exhaust pipe bend and fill the exhaust pipe and penetrate mto the engme via the exhaust pipe bend. In order to prevent this, it is known to install a vacuum valve m the seawater conduit when die seawater level is a certam amount below or above the exhaust pipe bend. The valve seals against the surrounding air due to the overpressure in the seawater when the pump is working but opens to the surrounding atmosphere due to the underpressure which arises when the engme is shut off. This prevents any siphon effect m the seawater conduit Vacuum valves are, however, susceptible to clogging and can fail resulting m water penetrating into the engine. The purpose of the present mvention is to achieve a seawater and exhaust system of the type descnbed by way of introduction which protects the engme from water penetration, without using valves with moving parts. This is achieved according to the mvention by virtue of the fact that the outlet conduit has a highest point which hes higher than the waterline of the boat, and that This is achieved according to the invention by virtue of the fact that the outlet conduit has a highest point which lies higher than the waterline of the boat, and that at least that portion of the outlet conduit which extends from the highest point and down to the exhaust conduit, has a flowthrough area which is greater than that required by the capacity of the pump. This design provides a conduit in which a siphon effect cannot occur. The conduit has a cross-sectional area in relation to the water flow which is so great that air/ exhaust can easily pass from the exhaust system up to the highest point in the con- duit and permit the conduit to be emptied of water. The siphon effect is thereby prevented and the risk of water penetration into the engine is thus eliminated without using valve devices which can fail due to clogging. The invention will be described in more detail with reference to examples shown in the accompanying drawing, where Fig. 1 shows schematically a marine engine in¬ stallation, and Fig. 2 shows an enlargement of a portion of the installation in Fig. 1. In Fig. 1. the numeral 1 designates a boat bottom and 2 designates a transom joined thereto. On an engine bed 3 fixed to the bottom 1 , an engine 4 is mounted on engine cushions 5. The engine 4 has a seawater pump 6 which has a suction conduit 7 connected to a bottom port 8 and a pressure conduit 9 connected to the inlet 10 of a heat exchanger 11 for cooling the coolant ofthe engine. An outlet conduit, gene¬ rally designated 12, connects the outlet 13 ofthe heat exchanger 1 1 to the inlet 14 of a water-jacketed so-called "exhaust pipe bend " 15, as is shown in more detail in Fig. 2. From the exhaust pipe bend 15, an exhaust conduit 16 extends via a muffler 17 to an outlet 18 for water and exhaust in the transom 2 ofthe boat. The aft portion of the exhaust conduit 16 is made as a so-called " swan ' s neck" 19. the highest point of ~> which is higher than the water level 20. i.e. the actual waterline of the boat, in order to prevent water from penetrating backwards into the engine from the outlet 18. In order to prevent water, by a siphon effect via the sea water pump 6. the conduit 9, the heat exchanger 1 1 and the outlet conduit 12. from filling up the exhaust pipe so that water will penetrate into the engine, the outlet conduit 12 is made in a manner which prevents the siphon effect. As is most clearly evident from Fig. 2, the outlet conduit 12 consists of a first verti- cally directed conduit section 12a and a second vertically directed conduit section 12b of greater diameter than the section 12a. These are joined to each other by means of a U-shaped connector piece 21, which - as can be seen in Fig. 2 - lies above the sea water level 20. The cross-sectional area ofthe conduit section 12a is dimensioned for the waterflow. i.e. for the capacity of the pump, while the flow- through area ofthe conduit section 12b is greater than that required by the pump capacity. In a practical embodiment with a waterflow of 30 liters per minute, a conduit section 12a with a diameter of 15 mm and a conduit section 12b with a diameter of 25 mm were selected. The conduit section 12a can of course have the same diameter as the section 12b. What is important here is. on the one hand, that the highest point 21 of the outlet conduit 12 is above the water surface 20 and. on the other hand, that the conduit 12b from the highest point and to the exhaust pipe bend 15 has such a large flowthrough area relative to the waterflow that air and exhaust can pass from the exhaust system up to the connector piece 21 when the engine is shut off.

Claims: Claims 1. Seawater- and exhaust system in a marine engine installation, comprising a water pump, a suction conduit connected between the water pump and a water inlet, a pressure conduit connected between the water pump and an inlet to a heat exchanger, and an outlet conduit which is connected between an outlet from the heat exchanger and an inlet to an exhaust conduit lying completely or partially beneath the waterline ofthe boat, characterized in that the outlet conduit (12) has a highest point (21) which lies higher than the waterline (20) of the boat ( 1, 2), and that at least that portion (12b) ofthe outlet conduit which extends from the highest point and down to the exhaust conduit, has a flowthrough area which is greater than that required by the capacity of he pump. 2. Seawater- and exhaust system according to Claim 1 , characterized in that the portion (12b) ofthe outlet conduit extending downwards from the highest point to the exhaust conduit has a greater flowthrough area than that portion (12a) which extends upwards to said highest point. 3. Seawater- and exhaust system according to Claim 1 or 2. characterized in that the outlet conduit has an upwardly directed conduit section (12a) and a downwardly directed conduit section (12b) joined at their highest points to each other by means of a connector piece (21), and that the downwardly directed conduit section ( 12b) has a greater flowthrough area than the upwardly directed conduit section ( 12a). 4. Seawater- and exhaust system according to one of Claims 1 - 3. characterized in that the outlet conduit (12) opens into a water jacket about an exhaust pipe bend ( 15) connected to the engine.

Inventors: LARSSON STIG, UHLANDER LENNART, LARSSON, STIG, UHLANDER, LENNART
Applicants: VOLVO PENTA AB, AB VOLVO PENTA
Application year: 1996
Main classification: B63H21
IPC codes: B63H21, F01N3, F01N7, F01P3