Volvo Penta D4 Operator's Manual page 27

Friction brake
The control has a friction brake which can be adjusted as
necessary to provide lighter or heavier lever action.
Adjusting the friction brake:
1. Stop the engine.
2. Mover the control lever forwards so that the groove in
the hub of the control lever is accessible.
3. Position a screwdriver in the groove and remove the
plug.
4. Adjust the friction brake (8 mm wrench):
Clockwise = heavier lever action
Counter clockwise = lighter lever action.
5. Reinstall the plug.
Controls
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