Mercury troubleshoot

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skhampton21

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Oct 3, 2005
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hey there guys,<br />I have twin 1998 150 CXLs (saltwater). Today after a so so fishing day I noticed I could not get over 2000 rpms with one motor but only while in gear. It would run perfectly to high rpms in neutral. But once in gear it would die out. Does this sound like a carburetor or spark plug problem? thanks in advance for any suggestions or help
 
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Perfidiajoe

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Re: Mercury troubleshoot

Having duals is a great diagnostic tool in & of it self. You can switch things back & forth to see what makes things happen. First I would make a visual inspection, fuel lines, plug wires, coils, fuel primer balls. When you say it won't go over 2000 rpm's is it missing, or just no power, are both fuel balls firm? Are all plugs firing? You don't say if it is carbs or injected, if carbs are they all getting fuel? Try pinning it down to a system, or eliminating systems known or proven to be ok. Post results, & more imformation about your engine, & problem. Good Luck, Joe
 
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wilde1j

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Re: Mercury troubleshoot

High RPMs in neutral don't tell you anything, except the motor is running. Sounds like possible fuel starvation. Make sure tank vent is OK, no air leaks in fuel pump suction lines, fuel pump diaphragm OK, no restrictions or blockages, etc. Try pumping primer ball while advancing the throttle. If it improves, definitely a fuel problem.
 
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skhampton21

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Re: Mercury troubleshoot

Originally posted by Perfidiajoe:<br /> Having duals is a great diagnostic tool in & of it self. You can switch things back & forth to see what makes things happen. First I would make a visual inspection, fuel lines, plug wires, coils, fuel primer balls. When you say it won't go over 2000 rpm's is it missing, or just no power, are both fuel balls firm? Are all plugs firing? You don't say if it is carbs or injected, if carbs are they all getting fuel? Try pinning it down to a system, or eliminating systems known or proven to be ok. Post results, & more imformation about your engine, & problem. Good Luck, Joe
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skhampton21

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Re: Mercury troubleshoot

Thank you so much for your reply,<br /><br />I am new to this outboard troubleshooting subject. The motors are carbureted. When the port motor reaches 1800 to 2000 rpms, it just dies back down to lower rpms. It loses all forward acceleration. So you essentially have to throttle down to keep from shutting off. Idles fine. Im thinking it is a fuel problem or spark plug issue. ALso, can I clean the carburetor out with any store bought spray or anything?<br /><br />thanks
 
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andy6374

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Aug 4, 2005
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Re: Mercury troubleshoot

To clean the carbs, you have to take them off the intake manifold, bring em home and disassemble them and them give em a good soaking in some liquid carb cleaner. Reassemble with new gaskets and you will be ready to. While you are at it, I would do the other set of carbs as well. That way they have the same maintainance.
 
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wilde1j

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Re: Mercury troubleshoot

If you plan to do your own repairs, I would suggest you get an OEM shop manual, if you don't already own one. Trouble shooting is covered very nicely there as well as correct repair procedures.
 
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Perfidiajoe

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Re: Mercury troubleshoot

As Andy said, you can do the other set, but I would wait if you are not to famillier with this, it's good to have a working model when reinstalling. Having the book or a few books is the way to go,( Factory manual is best, but some books explain better than others), Get as many as you can borrow, or at least look through, buy what's best for you. A good place for after market books is the library, go in & look.
 
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Perfidiajoe

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Re: Mercury troubleshoot

A quick test you can try, if the boat is in the water, run the engine when it starts to lose power, hit the choke for just the shortest instant, does the engine pick up? If it does, it will most likely be a fuel problem. With someone else running the boat, gently with your hand cover each carb in turn momenteraly, to determine which carb is giving trouble. They used to sell in auto stores a cheap spark tester, looked like a pen, with it you can see if all plugs, at least to the wire are firing. Can do the same w/ an inductive timing light. Good Luck, Joe
 
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