diff --git a/Tools/autotest/default_params/vee-gull_005.param b/Tools/autotest/default_params/vee-gull_005.param
index ab340c7eaf..9415f055bd 100644
--- a/Tools/autotest/default_params/vee-gull_005.param
+++ b/Tools/autotest/default_params/vee-gull_005.param
@@ -620,7 +620,7 @@ SIM_BATT_VOLTAGE,12.6
 SIM_DRIFT_SPEED,0.05
 SIM_DRIFT_TIME,5
 SIM_ENGINE_FAIL,0
-SIM_ENGINE_MUL,1
+SIM_ENGINE_MUL,0
 SIM_FLOAT_EXCEPT,1
 SIM_FLOW_DELAY,0
 SIM_FLOW_ENABLE,0
diff --git a/libraries/SITL/SITL.cpp b/libraries/SITL/SITL.cpp
index b4541b822d..3adb9cc673 100644
--- a/libraries/SITL/SITL.cpp
+++ b/libraries/SITL/SITL.cpp
@@ -78,8 +78,8 @@ const AP_Param::GroupInfo SIM::var_info[] = {
     // @Param: ENGINE_MUL
     // @DisplayName: Engine failure thrust scaler
     // @Description: Thrust from Motors in SIM_ENGINE_FAIL will be multiplied by this factor
-    // @Units: ms
-    AP_GROUPINFO("ENGINE_MUL",     8, SIM,  engine_mul,  1),
+    // @Range: 0 1
+    AP_GROUPINFO("ENGINE_MUL",     8, SIM,  engine_mul,  0),
     // @Param: WIND_SPD
     // @DisplayName: Simulated Wind speed
     // @Description: Allows you to emulate wind in sim
diff --git a/libraries/SITL/examples/SilentWings/Params/Rolladen-Schneider-LS8b.param b/libraries/SITL/examples/SilentWings/Params/Rolladen-Schneider-LS8b.param
index 98d5e0b7a0..ccba94be53 100644
--- a/libraries/SITL/examples/SilentWings/Params/Rolladen-Schneider-LS8b.param
+++ b/libraries/SITL/examples/SilentWings/Params/Rolladen-Schneider-LS8b.param
@@ -612,7 +612,7 @@ SIM_BATT_VOLTAGE,12.6
 SIM_DRIFT_SPEED,0.05
 SIM_DRIFT_TIME,5
 SIM_ENGINE_FAIL,0
-SIM_ENGINE_MUL,1
+SIM_ENGINE_MUL,0
 SIM_FLOAT_EXCEPT,1
 SIM_FLOW_DELAY,0
 SIM_FLOW_ENABLE,0
diff --git a/libraries/SITL/examples/SilentWings/Params/Schleicher-ASW27B.param b/libraries/SITL/examples/SilentWings/Params/Schleicher-ASW27B.param
index 960c2c713c..353379fa5a 100644
--- a/libraries/SITL/examples/SilentWings/Params/Schleicher-ASW27B.param
+++ b/libraries/SITL/examples/SilentWings/Params/Schleicher-ASW27B.param
@@ -632,7 +632,7 @@ SIM_BATT_VOLTAGE,12.6
 SIM_DRIFT_SPEED,0.05
 SIM_DRIFT_TIME,5
 SIM_ENGINE_FAIL,0
-SIM_ENGINE_MUL,1
+SIM_ENGINE_MUL,0
 SIM_FLOAT_EXCEPT,1
 SIM_FLOW_DELAY,0
 SIM_FLOW_ENABLE,0