Cummins engine idle adjustment

M

Matt

Member
May 6, 2008
97
Braintree, Ma.
Boat Info
400 Db
Engines
Cummins 6cta8.3m 450
I have been trying to find out how to set the idle on my Cummins 6cta8.3m engines? When they are warmed up they both idle at around 600 rpm in neutral but in gear they idle at 500 rpms which is not bad for docking but if I goose the throttle of one or the other I can have stalling at times.
The Cummins tech told me that in gear they should be idling at 650 rpm when I had the survey done but I have no idea how one goes about adjusting the idle speed.
I posted this on Boat Diesel but no one has answered so can anyone here tell me how to set the idle?
 
I am not sure about your engines, but I have the qsc500's, and I idle at 600 rpm's in gear. The boat has a electronic "slow idle" setting that drops it down to 550 rpm's. I was told not to shift the boat in slow idle mode as the boat could stall, so my guess is you dropping down to 500 is too low. I use that setting when in long 5mph zones only, as I am at almost 7mph in gear otherwise and throw a decent wake. I am not aware how the idle is adjusted, however. Good luck!
 
i have an idle speed rocker switch...also, the smartcraft computer can be adjusted but u will need the manual
 
I believe your engine is non-electronic and has a mechanical fuel system, is that correct? If so, your idle adjustment is on the fuel injection pump. I had the engine I'm thinking about and there were two idle adjustment screws, one for high idle (leave alone) and the low idle which can be turned (in, I think) to increase the idle. All this may be dependent on the exact make and model of the injection pump which can be different inside the engine line. If you will post or PM me one of your Engine Serial Numbers (ESN) I believe I can find the procedure for you; I have a subscription to Cummins' "QuickServe Online" which allows for entry of up to 5 engines's serial numbers for access to lots of manuals as well as parts documentation and am only using 2 slots.
 
Thanks for the help.

I had a Quickserve account but could never get to any service information. I called Cummins but they were not very helpful.

The engine serial numbers are port 46088059 and starboard 46089585.

I found some info on Tony Athens web site but have not had time to try it yet.

Thank again,
Matt
 
Matt, just sent you a PM with the procedure. I've found QuickServe to be a great resource but it does have a very crappy user interface. It's got all the engine documentation I can think of if you can get to it, but you have to have a paid subscription to do that. BoatDiesel is usually great for advice as well.
 
Matt,

Since I cannot post a picture that will allow you to understand how to adjust the idle on your engines, if you send me a quick note I will send them direct..


Tony
 
I know an owner of a 460 that needs the same adjustment. Boat idles at around 450 in gear which shakes the boat violently so we always goose the throttle up to 650. Please share the info.
 
Carver370 said:
I know an owner of a 460 that needs the same adjustment. Boat idles at around 450 in gear which shakes the boat violently so we always goose the throttle up to 650. Please share the info.
Click to expand...


PM me with an email address and I will send the file to you as well.
 
I would be interested in the procedure as well, if it applies. I have a pair of QSC8.3 engines with electronic controls. After a recent repair, my port engine is now idling at 100rpms higher. I have a slow idle rocker switch and when set both engines are in sync. The manual for ETS seems to indicate you can set the idle from the throttle controls. Can anyone confirm, if so, outline a decent procedure for doing so.
 
Tony sponsors the Boatdiesel.com website- and he is the "man" when it comes to Cummins...
If you own a diesel boat, it's the best $20 you'll ever spend.
 
Louisrose said:
I would be interested in the procedure as well, if it applies. I have a pair of QSC8.3 engines with electronic controls. After a recent repair, my port engine is now idling at 100rpms higher. I have a slow idle rocker switch and when set both engines are in sync. The manual for ETS seems to indicate you can set the idle from the throttle controls. Can anyone confirm, if so, outline a decent procedure for doing so.
Click to expand...


Louisrose, I think this is what you may need if you have these switches, it's from the Cummins 8.3 Recreational Marine Owner's Manual:

Engine Speed Control

The engine speed control (rpm ±) switch (2) allows the idle speed to be adjusted in 25-rpm increments by pressing the rocker switch.
Pressing the top of the switch increases (+) engine rpm.
Pressing the bottom of the switch decreases (-) engine rpm.
NOTE: Use slow deliberate clicks to increase or decrease the engine rpm.

When the RPM ± switch (2) is used with the engine at idle , the switch will only work from 600 to 1000 rpm.
NOTE: The RPM ± switch (2) will not change the idle speed when the engine is in SLOW- IDLE mode.

Use of the SLOW- IDLE feature will deactivate the RPM ± feature.
15200038_sm.png




If the engine speeds between the two engines are not the same, adjust both engines to the minimum rpm setting, 600 rpm, by depressing the bottom (-) of the switch until both engines are at 600 rpm.
Then using the RPM ± switch (1), adjust the idle to the desired speed, rpm.
15200039_sm.png


If you can't see the pictures PM me with an email address and I can send you a file.
 
alnav said:
Louisrose, I think this is what you may need if you have these switches, it's from the Cummins 8.3 Recreational Marine Owner's Manual:

Engine Speed Control

The engine speed control (rpm ±) switch (2) allows the idle speed to be adjusted in 25-rpm increments by pressing the rocker switch.
Pressing the top of the switch increases (+) engine rpm.
Pressing the bottom of the switch decreases (-) engine rpm.
NOTE: Use slow deliberate clicks to increase or decrease the engine rpm.

When the RPM ± switch (2) is used with the engine at idle , the switch will only work from 600 to 1000 rpm.
NOTE: The RPM ± switch (2) will not change the idle speed when the engine is in SLOW- IDLE mode.

Use of the SLOW- IDLE feature will deactivate the RPM ± feature.
15200038_sm.png




If the engine speeds between the two engines are not the same, adjust both engines to the minimum rpm setting, 600 rpm, by depressing the bottom (-) of the switch until both engines are at 600 rpm.
Then using the RPM ± switch (1), adjust the idle to the desired speed, rpm.
15200039_sm.png


If you can't see the pictures PM me with an email address and I can send you a file.
Click to expand...
Thanks very much. This procedure worked. The complication that was confusing me was that the idle adjustment only worked to increase RPM not lower . Finally i decided to check if there was a switch problem. Sure enough the +/- switch connection was loose. After adjusting in, the procedure worked fine.
 
QSC in low idle mode WILL NOT STALL when docking. Thats why u have low idle!! ( to tame the VIBRATING BEAST BELOW ) 5 years of service never stalled once !!!

Rob
 
I'm on an older generation Cummin's 450's but the idle adjustment is a very simple affair that can rattle free. Reset with a lazer rpm meter, and lock it tight and then add a backing nut.
 
I am trying to locate the part number for the low idle switch and the idle +/- switch. For 2007 44 Sedan.
0EF6B356-9322-4D24-961C-FA51A0C7FC97.jpeg
 
Cmoroff@hotmail.com said:
I am trying to locate the part number for the low idle switch and the idle +/- switch. For 2007 44 Sedan. View attachment 91771
Click to expand...
A quick search seems to indicate the switch pad is sold as an assembly, SBMAR has them for $795:
https://www.sbmar.com/product/cummins-marine-c-cruise-switch-panel-3969781/

I don't think there is anything special about the switches, though and it should be possible to purchase standard illuminated rocker switches and just rewire. Here's one from Amazon for $17:
https://www.amazon.com/Lighted-Rocker-Switch-DPDT-Connections/dp/B007PB7JDI
 
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