3.0 LX Mercruiser Bogging Down

ivescl

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May 28, 2003
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I have a 1994 3.0 LX Mercruiser which idles great and runs W-O-T like a dream, but when I run a low RPM (like in a no wake zone) she wants to bog down and die, usually at the same RPM range. Any help or advice would be greatly appreciated.<br /><br />Thanks :)
 

ivescl

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Re: 3.0 LX Mercruiser Bogging Down

Also, does anyone know which amp fuse should go between the gas guage and the ignition switch?
 
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Re: 3.0 LX Mercruiser Bogging Down

Charlie,<br /><br />I've got a 1988 Mercuiser 3.0 that is doing the same thing. It runs fine until the engine is warm and then at idle it wants to stall out, especially when I put into gear. Pretty frustrating when I'm trying to get it back on the trailer.<br /><br />If you don't mind I'm gonna watch your post here to see what response you get. If I find out the problem on my own I'll followup with ya.
 

Bondo

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Re: 3.0 LX Mercruiser Bogging Down

I'd be looking to the carb.... Float levels ??? Sounds like you're running Rich in the idle circuit....<br /><br />5 amp fuse should carry a fuel gauge....
 
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Re: 3.0 LX Mercruiser Bogging Down

Charlie, I haven't discovered the true solution to my problem yet but found that I had a crack rotor button. It was hard to notice until a touched the side to see how secure it was and the side fell off.<br /><br />A guy at work had told me to check the distributor. His boat had acted in a similar way and he had discovered a hairline crack in the distributor. When the distrib heated up it expanded and made the problem worse.<br /><br />I'm doing a complete tuneup today. :confused:
 

ivescl

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Re: 3.0 LX Mercruiser Bogging Down

I did a full tune-up about a month ago including new plugs, wires, cap, and button. The problem was there before the tune-up, but didn't get any better (or worse) after. I'm going to play with the carb and choke this weekend and see if I can find the key. Keep the suggestions coming. All help is greatly appreciated!! :cool:
 
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Re: 3.0 LX Mercruiser Bogging Down

I completed a full tune-up prior to reading your last post, Charlie. It didn't make a bit of difference either even with replacing the cracked rotor button.<br /><br />I beleive I have the Merc 2bbl carb. How difficult is it to rebuild? I've rebuilt a tractor carb 1bbl but upon appearances seemes quite less complicated that the one on my boat.
 

iwldntli2u

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Mar 17, 2003
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Re: 3.0 LX Mercruiser Bogging Down

The Merc 2bb are fairly easy. Just pay attention to your measurements (Float, Pump arm, Choke arm) and you will be fine. Keep everything orderly so you can replace things and put them back were you found them. When you strip it down complete, Soak it in gas or carb cleaner overnight. <br />If you need any help let me know-
 

Juancho

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May 18, 2003
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Re: 3.0 LX Mercruiser Bogging Down

I am not convinced that your carburetor is causing the problem. If it is, it sounds like only the idle circuit is acting up. Whenever I have had the sort of problem, regardless of what kind of motor, 9 time out of 10 if was a vacuum leak. A sure-fire way to confirm a vacuum leak is to try and adjust your carb, especial the idle mixture screw. If no amount of adjusting helps, it is definitely a vacuum leak. Time to change the intake manifold gaskets and the carburetor gaskets. Good luck.
 

ivescl

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Re: 3.0 LX Mercruiser Bogging Down

Wouldn't a vacuum leak cause problems at all RPM's instead of just the lower? Could this issue be caused by the fuel pump?<br />We've had terrible weather the past couple weekends here in NC, so I haven't had a chance to put my boat in the water and do any work, but hopefully this weekend will be better.
 
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Re: 3.0 LX Mercruiser Bogging Down

Well, I'm back. I have solved some of my problem.<br /><br />I talked with a service guy at a local marina and he suggested replacing the plug wires and adjusting the idle mixture. The plug wires did make some difference, but not enough in my opinion. <br /><br />I told him I had adjusted the idle mixture screw to the recommended 1 1/4 turns. He told me to adjust the idle mixture with the engine running and listen for the best setting. I did this and it has made a difference! No stalling out. :D <br />I also spoke with the previous owner again. He said that he had not used the boat in 3 yrs and he figured I was "running that old gas out." I take this to mean he did not drain the tank or clear the carb, so I imagine they're pretty gummed up. <br /><br />What is the best way to remedy this without tearing into the carb? Can I run a gas additive? What brand is best?
 
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