Cummins throttle

We got a Cummins marine diesel 6.0 liter model 450C in our boat...

The throttle quit idling down, stays a couple hundred RPM over idle when you push the cable all the way down. Makes it a PITA to go from neutral to in gear and near impossible to dock.

I've checked the cable to throttle lever linkage and that's good. This throttle lever is intentionally made with some slack in it. We've learned to push on this part to get to idle but you have to pull the hatch.

I'm thinking there must be a return spring someplace on the throttle assembly that has popped off. Anybody know this particular engine or know where to download a manual that would show the entire linkage?


Reply to
Karl Townsend
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No answers, just some questions to ponder.

You've already done the obvious and looked for little holes for springs to clip into, and for dead bits of spring buried in the grease at the bottom of the engine compartment?

Could it just be that your throttle lever on the engine is a bit sticky?

How do you know that the cable is intentionally a bit slack? Could it have slackened off over the years?

Reply to
Tim Wescott

yep. Working in a boat bilge is a bit of a challenge.

well, that's the problem. you can take the cable off and it won't return to idle, it has to be pushed down. I'm used to my tractors, take the linkage apart and there's a fair bit of tension, induced by a spring, to return to idle.

The cable is fine. Its a VERY HEAVY duty unit. I am puzzled by the lever that has a ball and socket with a bit of play. My guess is this is to decouple vibration but I'm not sure. I took it apart and it sure looks like it still functions as designed.


Reply to
Karl Townsend

It appears that you have "Morse controls", as you say, a heavy duty flexible cable", usually red in color. There are several rod ends that fit this sort of cable, one of them being a ball and socket end which does have a small amount of play, however this is not your trouble.

Basically a Morse cable is used as it pushes as well as pulls so be sure that the cable length adjusted to give full throttle arm movement. Gross adjustment by moving the clamp where the cable clamps to the engine, fine measurement by screwing, or unscrewing the rod end (there should be a lock nut to lock the rod end).

I'm not sure whether your engine has the older Cummins fuel control but it is likely that it has the newer CAV pump which has low and high speed stops to limit the movement of the lever. Adjust the throttle cable to ensure that when closed the cable applies (very) light pressure against the lever to hold the throttle closed. Once that is set check that you get full fuel with the cockpit throttle in the full speed position.


John D. Slocomb (jdslocombatgmail)

Reply to
J. D. Slocomb

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