Mercury runs half speed until hot

by Art
(West haven ct)

My Mercury outboard thunderbolt 50 hp runs at half speed for about 20 min then it takes off like a bat out of hell. It has new plugs sprayed the carbs with Mercury power stroke star bright in tank, new fuel line, did it last years sprayed it then ton of black smoke came out it popped and ran smooth for the rest of the summer, this year same problem , Any idea

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Jun 25, 2014
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by: Bruce

Hotter temperature may be closing a small vacuum leak. Take a piece of vinyl hose and stick one end inside your ear and take the other and run it along the gaskets that you can see and if it is sucking air you will hear it through the plastic hose.
You will have to find the vacuum leak before the engine gets hot

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