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    Octane booster

    My 850 thunderbolt has been suffereing from starting problems and I have been informed that it could be due to the use of the lower octane fuel (unleaded)I have been told that the older Mercurys this one is 30 years old need a higher octane fuel.As higher octane fuel (4 STAR) is no longer...
  2. H

    850 Thunderbolt starting problem

    Hi, I hope someone out there can help. I own a 1975 850 Thunderbolt Blueband. I have owned this motor for some ten years and has never let me down. At the start of this season I had the motor serviced as normal. As the weeks have progressed the motor is becoming harder and harder to start. There...
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