Throttle Return Spring | HYDROPHASE LLC

Throttle Return Spring

Mercruiser 5.7L linear throttle return spring

A “linear” throttle return spring on a 1992 Mercruiser Competition Ski 350 Mag Inboard engine.

Mercruiser 4.3L MPI coiled throttle spring

A “coiled” throttle return spring on a 2012 Mercruiser 4.3L MPI engine.

Do I need a throttle return spring for my boat?

The Ridesteady speed control system requires “throttle return force” so that when the throttle motor lets out cable, the engine’s throttle arm will pull out the slack and thus respond in-kind. Most marine engines have a throttle return spring assembled to the carburetor or throttle body. Some are easy-to-locate linear springs while others are less obvious coiled springs.

However, many Mercruiser carbureted engines (including TKS - turn key start) have inadequate throttle return force. These engines often require a throttle return spring be added in order for Ridesteady to work properly. Note that Mercruiser MPI and many Mercruiser 5.7L engines typically have a throttle return spring built-in.

The easiest way to determine whether you have a throttle return spring on your boat’s engine is to locate it visually. It will typically either be a long linear spring connected to the throttle arm on one side and a fixed location on the other, or a coiled spring on the inside of the throttle arm.

If you’re unable locate a throttle return spring visually, you can check for the effects of one. Simply disconnect and remove the throttle cable from the throttle arm shaft, typically by removing a nut. Using your finger, push the throttle arm back manually. When you remove your finger, if the throttle arm snaps back with moderate force, there is likely a throttle return spring installed. If the throttle arm doesn’t snap back, or it snaps back “weakly”, then a throttle return spring will need to be added.

If you’re unsure about whether you need to add a throttle return spring or not, we suggest adding one to your order just in case.