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Old 06-21-2008, 08:54 AM
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Location: Virginia
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Default Mercury 90 4-Stroke Low Highend RPM

My 2005 Mercury 90 4-stroke was put to bed last winter with a full tank of gas with plenty of Stabil. It was running at 6000 rpm when it was put up for a mild winter. This spring it cranked fine, would hit an RPM hesitation at about 3500 RPM and again at 4900 rpm. Put a can of SeaFoam in the tank and about 8 gal of new gas and the hesitations went away but I can't get above 5200 rpm. Any suggestions? Thanks in advance.
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Old 06-21-2008, 03:14 PM
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Possibly a plugged carb. May need to clean carbs.
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Old 06-22-2008, 08:56 AM
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Default Solution to Low RPM

Solved my own problem....called the dealer and he said "bring it in and we will charge you $185 to look at it!" so....I went to Advance Auto Parts and got four sparkplug...then to a local boat dealer and got a fuel filter. My wife and I then spent a nice afternoon at the lake. Changed the fuel filter and put new plugs in. Then a quick test drive and RPM hit 6000 without a bit of hesitation.

When I took the plugs out and checked the wear patterns on the plug tips there was a distinct difference in the #1 cylinder plug and the other three. #1 was much darker and had carbon buildup on the plug.

Easy fix that worked great.

SML
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