What grade of fuel should I run?

I recently purchased a boat (first time owner) and need to ask your advice on fuel grades to run. The dealer told me to run Premium 97+ octane, but I have since been doing some checking and Mercury recommends 87 octane minimum. I have been told these motors are extremely sensitve to ethanol and to use the lowest ethanol content possible. I know a lot of times they use ethanol to increase the octane in gasoline, meaning the lower the octane the safer I would be (in my opinion). The motor is a 2006 Mercury 225 Pro XS Jet. Your thoughts an advice is much appreciated.

I don't know a lot about Mercs but I am pretty sure 87 is just fine. I didn't realize there even was 97 octane? I think premium is 93. I run 87 octane non ethanol in my motor. There are a few places near me that sell non ethanol but you pay a higher price for it. I would advise you to stay with 87 from what I know. But if it is a new Merc I could be wrong since I do not know them well at all.

I run 87 in my Yamaha as that's what the book say's.

Johny25 said:

I don't know a lot about Mercs but I am pretty sure 87 is just fine. I didn't realize there even was 97 octane? I think premium is 93. I run 87 octane non ethanol in my motor. There are a few places near me that sell non ethanol but you pay a higher price for it. I would advise you to stay with 87 from what I know. But if it is a new Merc I could be wrong since I do not know them well at all.

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You can get gas with octane ratings of 100+. You might have heard it referred to as avgas because it's mostly used by the aviation industry for Cessna's etc. But it is out there if you want to run it in something. I've run some of it in my KZ1000 but not very much as I've heard it can/will burn valves up if you run it very long. I know several years back, people would use it to mix their racing fuel.

The biggest reason for avoiding E fuels that I've heard of is that the engines that were built prior to the widespread use of ethanol, have a problem with the rubber bits that come in contact with ethanol. The o-rings in the carbs, fuel pumps, fuel line etc start to deteriorate when exposed to it. The newer model engines are supposedly being designed and built with different rubber compounds to handle it.

Ok I have heard of fuel with octane that high just not at the local gas station JM. I didn't realize we were going to be discussing aviation and racing fuel lol..... was kind of thinking about normal everyday joe outboard operations.

Hey and by the way riverunner very nice first purchase on a fishing boat. That looks like a sweet setup! =D>

Thank you all for the replies! I think I will stick with running the 87 Octane and go with that. I am not sure why the dealer told me to run the high octane fuel. Most stations around here do only sell up to 93 octane, but there are two in our town that sell 97 (not sure why)....or at least they want you to believe it is 97 octane :---)

Johnny25, I have wanted a nice river boat for some time now. I never thought it would be THIS nice, but I found this deal on a consignment deal with a local boat store and couldn't pass it up. As far as I can tell (and others much more knowledgeable than myself) I have quite a few Ks less in it than the boat is worth. Always good to start in the green...even though it might not stay there ha! Ready for some warm weather!

:lol: Johnny, I just used the avgas as an example. Although I haven't seen one in a while, there are some gas stations out there that carry the higher octane fuels for what ever reason.

JMichael said:

:lol: Johnny, I just used the avgas as an example. Although I haven't seen one in a while, there are some gas stations out there that carry the higher octane fuels for what ever reason.

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don't know about running avgas in a boat motor, but I have run it in in my 427. the stuff I run is 100 LOW LEAD. so it apparently still has lead in it, not like UNLEADED gas. it definately boosts performance.
they also make octane boosters. maby by adding this to fuel you could bump up octane. I think I would just stick with the pump gas and maby add the ethenol fuel treatment. try the different grades, and see what happens. it may run perfect on the 87 octane.

I run premium with a shot of seafoam and green sta-bil in every tank for both my boats.

I've tried regular and had issues a few times with the hole shot and idle.

Anything without ethanol. Or at the very minimum, less than 7-10% ethanol.

turbotodd said:

Anything without ethanol. Or at the very minimum, less than 7-10% ethanol.

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Don't know where you're from as it doesn't say in your info but in many states it's not a requirement to post if their gas contains alcohol? Some stations around the major lakes here in KY advertise they have no alcohol in their fuel but...........??? Truthfully, I think they know that it will draw in the boaters. I've been meaning to buy one of the Briggs & Stratton Alcohol testers (part # 795161) and try it out at one of these places.

Run 87 octane, only a couple (the bigger super charged Verados) call for high octane.

If you can buy non ethanol then do it.

If you are going to have fuel in the tank for more than 3 weeks make sure to stabilize it with a marine grade stabilizer, and if it is ethanol use that stabilizer anyway.

Good luck

I've gotten in the habit of putting stabil marine (ethanol treatment, blue I think) in every time and using ethanol free fuel almost always. The big bottle of stabil has lasted me over a year at 1oz per 10 gal. I mix it heavier as directed when I think it's going to sit unused for a while. It's also good to keep the tank full to avoid condensation, especially when sitting idle for months. Hopefully this will keep me going a little longer. I've got a '78 Evinrude on my bigger boat that has countless hours on it. Every year I wonder if it's going to make it, but it just keeps going.