Vetus DEMPMP Silencer Installation Manual

Introduction

The Vetus exhaust system components are specifically designed for use in water-injected exhaust systems. The maximum continuous operating temperature for the plastic parts of these systems is 70°C (158°F).

It is recommended to install a temperature alarm to warn of excessively high exhaust system temperatures. If the quantity of injected coolant water is reduced to lower back-pressure, ensure sufficient water is injected when the engine is idling to prevent overheating. Insufficient mixing of coolant water with exhaust gases can also lead to high system temperatures. Good mixing is generally achieved with a nearly vertical exhaust injection bend. Poor mixing may occur with engines idling, especially if the coolant water injection bend is mounted nearly horizontally. If necessary, measures such as installing a water vortex or water splitter in the exhaust pipe can improve the mixing of coolant water with exhaust gases.

For water-injected exhaust systems, use a suitable quality hose. This hose must be reinforced, resistant to exhaust gases, high temperatures (100°C / 212°F), and oil. Good flexibility is essential for installation, and the hose must not collapse when heated. Vetus exhaust hoses meet these requirements.

Engine Power vs. Hose Diameter:

*Based on an allowed back pressure of 0.1 bar.

Safety Warnings

⚠️ WARNING: If water enters the engine from the exhaust silencer when the engine is stopped (e.g., during severe rolling or pitching of the vessel under sail), it will cause irreparable damage to the engine.

Excessive water in the silencer can impede engine starting; drain the water first. Excessive water can also be caused by repeated unsuccessful starting attempts.

Installation

Installing the DEMPMP Silencer

The silencer can be fitted either before or after the goose neck. Fitting it after the goose neck results in less gurgling exhaust sound. During operation, the silencer holds water, significantly increasing its weight, thus requiring adequate support. Silencers with hose connectors from Ø 40 to Ø 90 mm are equipped with two handles for securing. Silencers with a Ø 100 mm connector can be secured using the two supplied Ty-raps®.

Exhaust Pipe Installation

To ensure proper drainage of coolant water injected into the exhaust pipe, the pipe must be installed with a continuous downward slope from the water injection point to the silencer. The exhaust pipe contains water during operation, increasing its weight considerably, so it requires proper support. The exhaust pipe from the silencer to the transom connection must be installed such that:

• The highest point in the exhaust pipe is no more than 150 cm (60") above the underside of the silencer.
• The length of the pipe section between the silencer and the highest point does not exceed 300 cm (120").

Hose Connections

To facilitate fitting the hose onto the connectors, use only water and/or soap, not grease or oil-based products. Secure each hose connection with two stainless steel hose clamps, 12 mm wide.

Installation Examples

Pages 16 and 17 illustrate exhaust systems featuring silencers like LP/LSS/LSG, the DEMPMP silencer, a goose neck type LT, and a transom connection. The height difference in the goose neck effectively prevents water entry from the stern. When the engine stops, any remaining water in the exhaust pipe (between the system's highest point and the silencer) will flow back into the silencer. To minimize this backflow, the goose neck should ideally be installed directly above the silencer (see drawings 1 and 3). If the goose neck is mounted directly to the transom (drawings 2 and 4), the maximum length of the exhaust pipe between the silencer and the highest point must be considered.

Preventing Siphoning (Drawings 3 & 4)

If the water injection point 'C' is located below or less than 15 cm (0.6") above the waterline (even when the vessel is heeled), there is a risk that coolant water may enter the engine due to siphoning when the engine is stopped. This siphoning can be prevented in two ways:

1. By creating an air vent in the coolant hose between the engine block and the water injection point 'C', for example, by installing an air vent with a ventilation pipe.
2. By fitting an air vent (with valve) in the coolant hose between the engine block and the water injection point 'C'.

Diagram Descriptions for Installation Examples:

• Diagrams 1 & 2 (Pages 16-17) show typical Vetus exhaust system layouts with the DEMPMP silencer (MP), goose neck (LT), and transom connection. They indicate minimum clearances from the hull and maximum pipe lengths, for systems where the water injection point 'C' is 15 cm or more above the waterline.
• Diagrams 3 & 4 (Pages 17) illustrate methods to prevent siphoning. These diagrams are relevant when the water injection point 'C' is below or less than 15 cm above the waterline, showing two methods: creating an air vent in the coolant hose or fitting an air vent with a valve.

Maintenance

• Regularly check all hose connections for gas and water tightness.
• Drain the silencer before winter lay-up.

Technical Data

Silencer Principal Dimensions

The following table details the principal dimensions for various DEMPMP silencer models:

Note: Mounting hole dimensions (2 x Ø 6.5 mm) are shown in diagrams on page 18.

Rubber Exhaust Hose Specifications

Vetus offers rubber exhaust hoses with the following specifications:

The diagram on page 19 illustrates correct hose routing and installation, showing correct (✔️) and incorrect (❌) configurations.

A grey, cylindrical marine exhaust silencer with a ribbed outer casing is depicted on page 1.