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Recommended gas for 25hp 4 stroke bigfoot Mercury 2003?

CapnAhab

Member
I had big carb problems with this and recently changed it. My friend has the same motor and only uses racing style gas 98 oct no ethanol from the only station areound here that has it. It's ca $8 a gallon and that's what I've been using. Another station has "premium" without ethanol that 91 or 92 (I forget) for around $2. Would I be taking a chance of messing up the carb again by using this? Thanks
 
I find "gasoline" stations near lakes where marine engines are used. I find that the reason is that gasoline survives storage better than ethanol.....otherwise why the stations located where they are?

On 87 or 91, my Merc. OEM manuals state minimum octane is 87. My engines run on 91 including my small engines at home. No doubt, call it old wives tale or hocus-pocus, or superstition, they start better, idle better, and just run better. 91 runs around $275 which is cheaper than ethanol premium which likes the $3 number most places selling gas, even in this fuel glut where 87, 10% or less ethanol is running around a buck 40.

If you want to complete the job, get some NGK iridium plugs (cross referenced to what you are running in conventional plugs).... NGK catalog available online, and really notice some improvements....ebay sells them.
 
Thanks for the tip on the plugs. I hadn't heard about them before. I ended up getting 91 octane no ethanol unleaded at a local station. Their lower octanes have ethanol but this one has a sign saying no ethanol on the 91.
 
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