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Author Topic:   help!-75 hp Mercury stumbling
Mike in Seattle posted 07-13-2001 05:55 PM ET (US)   Profile for Mike in Seattle   Send Email to Mike in Seattle  
I've got a '95 Mercury on my whaler. While on vacation this week, I hit a wake and landed a little hard but nothing extreme. Immediately, the engine was sputtering and snorting and wouldn't rev up. It would idle roughly and would rev up out of gear but still, not smoothly. I changed fuel tanks and checked the oil tank.

After 10 minutes of this, it started to smooth out and would run okay above 3000 rpm but would start missing below that. Eventually it fixed itself and for the next 2 days it was fine. The last day, I hit another wake and it all started again. I'm home now and have checked everything I can on the trailer (link and synch, timing, loose connections, fuel filter) and everything seems okay. The other clue I can offer is that the plugs are oily (wet) every time I check them.

Any ideas of stuff to check before I head out to try it? Thanks in advance.


jimh posted 07-14-2001 09:51 AM ET (US)     Profile for jimh  Send Email to jimh     
It sounds like one or more of the plugs are not firing. If the whole ignition system were out, of course, it would not run. One cylinder not running will give a rough idle and limited power.

Check the actual connection to the plugs in the rubber plug boot. You may not have a good connection. The rough landing may have loosened a plug connection and perhaps you have not re-seated it all the way onto the top of the plug.

If there are separate coils/drivers for each plug, one of those may be loose or may be damaged.

Put your timing light pick up on each plug wire individually and verify that cyclinder is firing.

Let us know what you find. Gathering collective experience in trouble shooting engines helps all of us.


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