1992 Mercury 90hp 3 cyl intermittent wont run

boatdrinks554

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Jun 4, 2011
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4
Im pulling out my hair trying to get to the bottom of this. 90 percent of the time the motor starts fine and runs perfectly. Then after an hour or so of pulling wake boarders or just running around the lake the engine suddenly stops as if the key had been turned off. It will then crank but not start, then after letting it sit for halve an hour or so it may start right up with no problem only to stop again. Im thinking it maybe heat related and something going on in the ignition system. I've down loaded a few shop manuals, but im trying to figure out how to proceed and if anyone else has had this happen before. Plus because the problems intermittent trying to trouble shoot is unusually difficult.

Its a 1992 Mercury 90hp 3cyl.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1992 Mercury 90hp 3 cyl intermittent wont run

Take a timing light and ohm meter with you. Check the voltage while running and if it is overcharging the rectifier has a problem and is overheating the stator. If the charging is ok and when it happens check the spark. If you have no spark its the stator failing as switchboxes do not come and go,they just fail.
 

boatdrinks554

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Joined
Jun 4, 2011
Messages
4
Re: 1992 Mercury 90hp 3 cyl intermittent wont run

Sounds good, Im out trying to get it to fall right now so that I can test the system. I will test the items you mentioned. Thanks for replying :)
 

boatdrinks554

Recruit
Joined
Jun 4, 2011
Messages
4
Re: 1992 Mercury 90hp 3 cyl intermittent wont run

Ok just tested voltage while running at the battery an found it to be at 14.5V Right now I can't get the engine to fail, currently running it in a 100gal water tank in the drive way.
 

boatdrinks554

Recruit
Joined
Jun 4, 2011
Messages
4
Re: 1992 Mercury 90hp 3 cyl intermittent wont run

Ran the engine for almost 3 hours today, and it ran just fine. Problem is im wondering when this gremlin is going to show back up. The only thing I was able to see today was while running it in the water tank it tossed out a few tar balls from the engine. I had added some sea foam during the last fill up to try and clear up the fuel system.
 
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