Engine idle woes-Will not idle after warm

[Pa La O La]

Good day to all,

Have you ever? My question is I have a 3GM30 and she starts fine runs fine BUT after running for several hours she doesn’t like to idle. When restarted the next day or week she starts right up. No bleeding needed idles fine. What a pain trying to dock when you have to keep her revved up. No - if she does die she will start up again I just have to keep the throttle advanced. Shifting can be real fun. Any one have any ideas?
Thanks for any suggestions

Gary

[never monday]

How many hours on the engine? what RPM are you calling idle? some people have them set too low.

[Pa La O La]

Well,

I'd say the same as it's been for the three years I've had the boat. (Just info there no tude) I'd say around 9ish at idle & I run at around 24. It only becomes a problem after I've been motoring for awhile. Sea state isn't a factor. Hours sit at 992. It was around 850 when I got her.

[never monday]

With 900+ hours it's getting time to service the injectors. I'd also like to see you run it hard atleast once a quarter. 2800-3200RPM is what's normaly recomended. Have a look at you're fuel filters including the engine mounted filter. Most people forget about that one.

[Pa La O La]

Hey,

Had both off to inspect, looked for hole in pump diaphragm too. I guess my biggest question is why only when it's warm? I can leave it run at above idle (between 12 to 20) motoring tied at the dock. As an engine check before heading out on a cross the gulf passage. Runs fine. It is only after she has had a good work out that she doesn't want to slow down. Other than at the idle detent she works fine. Again the next day it's like every things is all better. Never tried a few hours later because it is usually after a passage and we are done for the day in more ways than one.

Gary

[Alan Wheeler]

Also check the lift pump filter. A much over looked filter. If there is one fitted that is. It is a light gauze and IMO is not required, providing you have good filters ecverwhere else. The pump filter is a pain to get at in an emergency and I remove them before the "emergency" arrises.
To the stopping situation, you need to be a little more accurate than "9'ish". Firstly, you need to ensure the RPM is correct to the indicator. If it is an electric meter that is. It will have a control for calibration on the back. Ensure it is correct. The difference of only a few RPM could be your problem.
Check the stop cable is fully home when running. If it is pulled slightly tight, it could be enough.
As Pat stated, at nearly 1000hrs, it would be a good point to have injectors serviced and as you have such a problem, I would suggest having the pump checked and calibrated at the same time. The pumps have springs internally that can change resistance with heat and sometimes break. Plus they have wearing parts and a calibration maybe required.