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Mercury outboard 1970 mercury thunderbolt 650 ran great last weekend but tried to start it this weekend and it won't start, it kinda pops and backfires through the prop and its got good spark in all cylinders?

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Posted on Jul 21, 2013


6 Suggested Answers


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Posted on Jan 02, 2017



  • 187 Answers

SOURCE: 1994 40 hp mercury force outboard with no spark

If the fuel was not treated with a fuel stabilizer than you probably have a varnish build up in the carburetor. This varnish will clog fuel needle valves and jets. You need to disassemble the carb to clean the jets and needle valves. Sometimes cleaner is not enough you need to us compressed air to blow out the jets. Good luck.

Posted on May 13, 2009


  • 3 Answers

SOURCE: 1986 9.9 Mercury Outboard Motor

Check plug wire first-- replace if bad. See if contact in plug cap is corroded. Use some Dielectric Contact Grease in the spark plug cap-- this will ensure good contact.

Also check kill wires that travel to tiller. They often get broken internally or get shorted out as they enter the housing engine.

These are the most obvious and easiest to fix. Your intermittent probem sounds like one of these issues (I used to have this same engine and had both problems)

Posted on May 17, 2009


  • 207 Answers

SOURCE: 1999 Mercury Mariner 9.9hp outboard motor

should be on the side with a lever but could you give me more info please

Posted on Jun 27, 2009


  • 2 Answers

SOURCE: 30 hp johnson outboard motor trys to start. It

1985 30 hp johnson used a cdi system(solid state, no points) check the power pack.

Posted on Mar 09, 2010


ray gallant

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SOURCE: where is the serial number on mercury 115hp 6 cylinder boat motor

Posted on May 01, 2010

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