Read the post on 3.0 "clucking" and that same mentioned sound makes me cringe. So I was wondering if anyone had any tips or tricks to setting the idle rpm's? I was thinking about putting it on the muffs and adjusting the idle screw, is this correct?
You really need to do it with the boat in the water and in gear.<br />The adjustment dependes on the linkage and year of the 3.0 you have, also weather it's an OMC or Mercruiser.
Don,<br />I have a 1992 3.0L Mercruiser. So Don I assume you try to hit the recommended range of 650rpm's while the boat is idling in forward gear? This would be done by turning the adjustment screw all the way in and backing it out accordingly. Am I on the right track? <br />By the way.....Don S you have been really great since day one of my joining this forum. A real pleasure to be a part of
sea<br /><br />i have a 1995 3.0 LX<br /><br />you have to read a manual its sounds simple but is harder than just turning a screw to do it right<br /><br />the manual recomends you disconect the linkage at the carb to set the idle<br /><br />you have to set the idle mixture screw on the carb<br /><br />and you have to be sure the cable is adjusted correctly or it wont get pulled to the idle stop the same every time <br /><br />i played with it before i had a manual and got bad results until i did it there way and what do you no it works right now<br /><br />tommays
Thanks tommays. I have access to a manual and will check it out. It seems like once you set the idle with the linkage disconnected the tricky part would be to connect it keeping the same settings
Sea Ray Steve<br />I agree follow the manual but sounds like people are talking about two different things. There is a idle speed adjustment and a idle mixture adjustment. Adjusted the idle mixture for the smothest running engine. Then with the engine in gear set the idle speed to where the engine will not die as you shift in and out of gears. After that increase it a little for a saftey factor. Idle speed and mixture with change with weather and elevation. Unlikely you will find a setting that will be right on the Ocean at sea level and Lake Tahoe at 6000 feet. If it is a EFI model then the module will adjust for you.
Boatist is right, the "Clucking" post was in regard to idle speed. <br />Below is a picture showing the location of the screw for adjusting the idle speed.<br /><br />EDIT: Removed statement about EST ignition and base timeing for carb adjustment... Wrong info.<br /><br />
Hi<br />If you connect the 2 white leads (that is not in use)on the distributor to each other, and connect the 2 leads that goes to the shift interupter to each other (on the harness side off the shift-interupter) the timing is in base mode.<br />This must be done with the power off.<br />Regards<br />Affa
Affa,<br />Thanks for the answer. Why can't the carb be adjusted with out setting the est to base? It seems to me, you turn the screw to the smoothest idle and your done. What makes going to base timing diffrent? Just wondering.<br />Thanks,<br />Bob
Hi Don,<br />So when I turn the idle adjustment screw a turn or two that changes the timing? How can that happen? I don't understand how one effects the other. Is that why I never get that smooth of an idle? <br />Thank You,<br />Bob R
Bob R<br />Glad you kept asking about adjusting the carb when in base timing mode.<br />I went to the manual to see if they gave an explantion of why, and to my surprise, I couldn't find anything about putting the EST into base timeing for carb adjustment.<br />Took about an hour, but I did find out that the 3.0L engines with the Mercarb and EST ignition, DOES NOT have to be in base timing mode for carb adjustment. That was actually in the Thunderbolt V ignition system.<br />I have gone back to my other posts in this thread and edited out the "Bad Information" I was handing out.<br />Sorry bout that guys....
Thank you Don. Now I just need to get the motor to idle a bit smoother. I idle it at about 750 in netural and it has a little shake. Can you share any tricks on making a 3.0 purr?<br />Thanks for your help.<br />Bob
No real secret, if you have good compression, no vacuum leaks. Cap, rotor, and spark plugs (other than Champion), and plug wires that are in good shape and a properly operating fuel system, it will idle great, for a 3.0L. If you are expecting it to idle as smooth as a new automotive EFI engine, forget it.
For those with the 1995 3.0 l or lx with the est ignition I have wasted a whole summer tracking a blown head gasket to a cracked intake/exaust manifold to a timming problem to a carb adjustment problem needless to say they were lessons well learned. But I still have not figured out why I cannot achieve proper timming advance once rpms are increased according to the merc manual it's always about 13 degrees above the recommended setting ( i have followed the timming proceedure to a "T") and all the ignition parts have been replace with factory marine grade replacement parts. Word to the wise never use after market ignition parts to save a buck it just isn't worth it. any suggestions to the timming advance problem I have replaced the module 3 times and tested them each time to be sure of proper operation.
Well fugitive, being unable to see your manual, is it revision 2 from 95? It should say on the bottom right of the cover.<br />Here is a service bulletin that may help.<br /> Service Bulletin 95-11<br /><br />You are putting it in base timing I presume.<br /><br />PS: It's really best if you start your own thread when you have a question like that. You could refeerence this post, but at least others will look at it because it's a new post and not an old one.
Guy's, if it is a car or a boat, a four banger will idle rougher than an 8 banger. With a four cylinder engine, the performance and condition of each cylinder is more critical than an eight cylinder. Before any "finishing touches" such as idle and timing, it is important to make sure the engine is healthy. At the very least a compression test is in order. After that, adjusting the mixture screws (low speed jets) for the highest smothest idle is in order. Then adjusting the idle down to specs for ignition base timing and checking the advance curve for propper timing advance is in order. Some engines, such as the 95 merc 4 cyl. require you to jump a couple of wires to get the dist. into the base timing mode....read your manual! After that, there is no choice than to have the boat in the water to do the final idle adjustment......muffs just wont work. After you have the carb adjusted right, make sure the throttle linkage is pushing the carb to the idle screw....adjust linkage if needed.
FYI:<br /><br />Speaking of "idle speed", I had a problem with my previous boat (Mercruiser 3.0) dieseling when it was new and when I tried to adjust the idle speed lower I found that the cable would not allow the idle screw to hit the stop. Adjusting the cable then allowed me to get an idle speed that cured the dieseling problem.
