97 Mercruiser 3.0LX Rough Idle

[CPro]

I have a hard time getting my 3.0 to idle well much below 900 rpm. It gets rough sounding, kind of lopes along and then eventually sputters out if I don't give it gas. I am referring to my boat tach...which I'm not sure how accurate it is. New plugs, new wires, just recently reset the timing...new fuel filters...relatively new fuel pump...and a few other things.

When I rebuilt the carburetor I was missing a new gasket for the venturi cluster..so I tried to reuse the old one. It probably isn't 100%...but was wondering how critical this gasket is?

Could this also just be a choke setting issue? Even once the engine warmed up, although it smoothed out some, it still wasn't real good at low rpm's

Another thing I'm wondering about is the correct setting for the accelerator pump. There are 3 settings for it & I'm not positive I have it set right. For what it's worth, the boat seems to accelerate fine. If I understand the function of the accelerator pump correctly, this shouldn't really have much to do for just establishing a good idle speed, should it?

Thanks in advance for any advice.....!

 

[fat fanny]

Re: 97 Mercruiser 3.0LX Rough Idle

With the accelerator pump I would just go with the stock location from before the rebuilf that's what I did and she jumps up just fine. The rough idel though depending on how bad it is could be numerous issues all 3.0 rumble a lil but it could be anything from fuel filters, fuel pressure, air idle mixture screw adjustment, tweaking the timming to suit idle and performance (doesn't always have to be set @ spec exactly) and down to numerous electrical connections which is where I would start after verifiying all the afore said issues starting with the main harness connector pull it apart and clean all the prongs and recpticles with a light emery and contact cleaner and then move onto all!!!!other connection doing the same thing starting with the main ground on the block you will be surised to what you will find and it's result especilly pay close attention to the connection to the coil and dizzy make sure thier solid tight connections and check continuity through all lead's "all" of them. I had a no spark issue over the weekend and after 8 hours of troubleshooting I found that the connections to the coil from the main harness and from the coil to the dizzy the internal female connections were loose and had to expand them with a paper clip with a little hook on the end to get a good solid connection and it improved my starting and performance from that little trivial issue so don't rule out electricals on issues like these. Sorry for being so long winded but sometimes that's what it takes time and patience. Good luck and post back