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Old 05-25-2011, 01:51 AM   #1
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Post Mercruiser 3.0LX Timing

I'm trying to set the timing on my Mercruiser 3.0LX. The manual tells me to install a jumper between the two white leads coming out of the 4 pin connector on the distributor to disable the timing advance, then set the timing to 1 deg BTDC. I am able to do this. It then tells me to remove the jumper and at idle, the timing should advance to 12 deg BTDC. Further, increasing the engine speed to 2500 RPM should cause an advance to 25 deg. I am not getting this advance when the jumper is removed. The boat seems to be running fine, but I haven't had it in the water yet. Not sure how it will perform under load. Am I doing something wrong, or do I have a bad distrubutor? Thanks for any help you guys can offer.
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Old 05-25-2011, 02:10 AM   #2
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well....stop the engine...check the inside of the distributor for any corrosion ...also check to see if the plate moves freely...it the timing advance.......check all connections....try putting the jumper back on and see where the timing goes....then follow the instructions again....there has to be something your missing...did it say that the timing will advance when the white wire comes off ??..or when you re-plug the plug back into the dist.???



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Old 05-25-2011, 02:15 AM   #3
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It says that the timing will advance when the jumper is removed. The manual doesn't give a very good description of how mechanically the timing advances, so not too sure what to look for. I did check the pick up coil and it tests good.
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Old 05-25-2011, 01:44 PM   #4
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I'm still looking into the advance issue, but found an old post (July '08) from Bayboy about a timing issue. He found that the timing had to be changed because of the ethynol being added to the gasoline. Has anyone made changes to timing based on the new fuel additives?
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Old 06-02-2011, 05:36 PM   #5
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I've sorted the timing problem out. I didn't have the timing advance blocked correctly. Engine is now running smooth. I am idling at around 950 RPM though and I think it should be around 650. Idle set screw is barely touching. Not sure what is going on, may have some gunk in the carb. Any suggestions?
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Old 06-02-2011, 06:22 PM   #6
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Correct, 950 is too high.

If the idle speed set screw is just barely touching still try to back it out to see if the idle speed drops. If it does not, try to move the carb linkage back towards the idle speed set screw by hand. If you can, and the idle speed then drops, I suspect some issue with the linkage or the cabling from the helm control.

If the idle still won't drop you'll have to dig deeper. Are the idle MIXTURE screws adjusted correctly? With the engine running at idle look into the top of the carb; do you see any gas dripping? Are you certain you followed the correct procedure/sequence for setting the timing and idle?

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Old 06-02-2011, 06:23 PM   #7
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Also, not sure if the carb has a "fast idle" cam built into the choke mechanism but, if so, make certain the choke is working, and disengaging, correctly.
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Old 06-10-2011, 12:39 AM   #8
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Default 3.0 engine Idle speed adjustment from the Mercruiser Manual

Boat In The Water Tests
ENGINE IDLE SPEED - CARBURETED MODELS
! WARNING
Do not leave helm unattended while performing idle speed check. Boat MUST BE moving
forward (not tied to the dock) when checking idle speed.
1. Start the engine and operate 10 to 15 minutes or until the engine reaches operating
temperature, and TKS quits drawing air and fuel through the intake.
2. Disconnect throttle cable from carburetor.
3. Start engine and place remote control lever in forward gear, idle position.
4. Adjust idle speed adjustment screw to obtain 750 RPM.
5. Stop engine. Readjust cable barrel and reinstall throttle cable.
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Old 06-10-2011, 03:22 AM   #9
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Quote:
Originally Posted by ss3964spd View Post
Also, not sure if the carb has a "fast idle" cam built into the choke mechanism but, if so, make certain the choke is working, and disengaging, correctly.
there are no fast idle sets in marine engines that are carbed.....

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Old 06-10-2011, 01:10 PM   #10
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Quote:
Originally Posted by seapuppy View Post
there are no fast idle sets in marine engines that are carbed.....SP
Interesting. Thanks Steve - learn something new every day.

Dan
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