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04'-70HP 2stroke-rough idle/power loss

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  • 04'-70HP 2stroke-rough idle/power loss

    New to the forum here, but have been lurking & reading your ideas & comments to others that have had similar issues/problems.
    Boat/motor new in 2004. Yamaha 70 HP TLRC - 2 stroke. Had problem before & had carbs rebuilt in Feb. of this yr.(2008) We go out saltwater & fresh water every 2 wks or so. I keep mouse ears on & start 2 or 3 times a week so gas doesn't sit in carbs for all that long.
    Last week out in Tampa Bay & motor won't start. Turns over but seems like it's not getting any fuel. Barely made it back in using *****ing motor. Got home & got it to start but ran very rough, coughed, sputtered, and would shut down after 10 seconds. Consistantly did this. Drained the gas tank, replaced fuel filter, changed all hoses up to & including the fuel pump itself.
    Put it in the lake and it would start, but still idled very rough & then would turn off. Couldn't even get into gear before it shut off. Finally after 10-15 minutes it started smoothly & ran like a charm for 10 minutes & then rpm went from 4800-5000 & dropped to 2300 rpm at full throttle. Would lug at low rpm for 5 minutes or so then suddenly surge back as if nothing was ever wrong.
    Help me please, I got really pissed at my wife because she asking "what was wrong & I thought that was fixed."
    Back at the house w/ mouse ears on it, I can get it to start w/ no problems but it will shut down in less than 10 sec, it will start right back up & shut down again. When I put it in gear & give gas it will go & sound somewhat smooth, but it's not right.
    I've read threads from "Wally" in Orlando & "Hamfisted" that have had similar problems. SeaFoam shock treatment was just purchased and I'll try that tomorrow. Berryman's Chemtool Spray will be after that if it doesn't work. Are there any electrical connectors/openings that would cause this. I thought that fuel was the problem especially w/ ethanol content in gas now days.
    Any help would be greatfully appreciated, and feel that this forum has a terrific group of individuals that take their time to help out "the Rookies" like myself. I live in Winter Haven, FL & can be reached at RHH138@aol.com
    Thanks, Bob Hayes

  • #2
    Does sound like fuel delivery... I assume you checked all hoses for leaks and checked and replaced water separator if you have one?

    Do you use a built in tank or 6 gal remotes. If built in was there ever a water issue? Could also be a fuel pump, but your problem sound very severe for that unless there is big tear in it...

    You may want drain you carbs before running seafoam. Brass plugs on the bottom sides. Careful not to drop them in the cowl and have paper towels on hand. May be junk sitting in the bottom, had this happen to me with a 90 2 stroke. It cleared up nicely....

    Try not to get pissed at the wife may be she like boating and is concerned...:-)

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