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  • Fuel

    I have a 2003 197/X7 and was wondering what everyone recommends for fuel. The previous owner used regular unleaded. Should I use what has been used in the past or is there a better option?

  • #2
    I used to use 93 Octane until Rec90, non-ethanol, became for readily available in my area.
    If its not a competition ski boat, its always second best.

    2008 MasterCraft X14, LY6, 400 HP
    1994 MasterCraft ProStar 205 (SOLD)

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    • #3
      I use what the boat calls for. Old boat called for 89 or better, newer one calls for 87. Both did fine.
      I switched to the non ethanol for last 10-15 gal at end of last year so that is what sat in over the winter.
      Will go back to 87 as soon as I get it, hope soon.

      Usage may affect decision as well.

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      • #4
        In my 2002 with the Predator/RTP , 89 octane (mid-grade around here) was my initial instruction from the dealer and I've run it from the start. I believe I checked the Indmar manual at one time, but honestly can't recall now.

        No non-ethanol in the vicinity for me, unfortunately.

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        • #5
          I have a 2001 prostar 209 with the Indmar 330 HP LTR and I believe the manual calls for mid-grade (89 octane) I generally always run the mid grade but have run regular from time to time when the dock doesn't have mid grade. I've also run premium when neither was available. Never had any problems.

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          • #6
            Mine calls for midgrade, but I run premium pump gas, usually 91. If I filled at a marine I would be buying midgrade as it’s ethanol free in that case.

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            • #7
              What motor?

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              • #8
                2004 197 RTP motor....manual suggests 89 octane or higher. Most readily avail non-ethanol is typically 91 so that's what I run

                Sent from my SM-G960U1 using Tapatalk
                Everyone Dies, but not everyone lives

                2004 Prostar 197, ACME 843

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                • #9
                  Originally posted by MIskiboat View Post
                  I use what the boat calls for. Old boat called for 89 or better, newer one calls for 87. Both did fine.
                  I switched to the non ethanol for last 10-15 gal at end of last year so that is what sat in over the winter.
                  Will go back to 87 as soon as I get it, hope soon.

                  Usage may affect decision as well.
                  This is a great answer. There's no benefit to using higher-octane fuel from what the engine was designed for. There is a chance of engine damage if you use lower octane. Most modern engines have a knock sensor that will adjust the fuel mixture before low octane can cause harm, but I wouldn't bet my engine on it. Adjusting the mixture for low octane also reduces HP.

                  Modern engines should also handle ethanol just fine. Ethanol can hold water, which is obviously a concern in a marine engine. That makes winterizing with non-ethanol gasoline a great idea.

                  There's an Indmar manual here: https://www.manualslib.com/manual/87...page=47#manual

                  Says 89 octane for standard engines and 91 for the LS7. Looks like a mid-2000s manual.

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                  • #10
                    Originally posted by JohnnyB View Post
                    2004 197 RTP motor....manual suggests 89 octane or higher. Most readily avail non-ethanol is typically 91 so that's what I run

                    Sent from my SM-G960U1 using Tapatalk
                    Non-ethanol around here is 89 and 90.

                    I don't run it because I have an LQ9 that wants 93 octane.

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                    • #11
                      Originally posted by MIskiboat View Post
                      I use what the boat calls for. Old boat called for 89 or better, newer one calls for 87. Both did fine.
                      I switched to the non ethanol for last 10-15 gal at end of last year so that is what sat in over the winter.
                      Will go back to 87 as soon as I get it, hope soon.

                      Usage may affect decision as well.
                      I always point out that if you take gasoline with ethanol in it add water and shake the ethanol will mix with the water and it will settle out of the fuel. Because of this what you really need to do more than anything when running ethanol is to dump your fuel water separator a few times a season into a mason jar and let it sit for awhile if you have any water/ethanol it will settle out show you that you are getting moisture in your fuel system.

                      This could be kids pouring water into your fuel tank, it could be the loop in your vent hose fell over, it could also be poor quality old gas from the local speedway. But if you keep on top of that the fuel system won't notice.

                      Watch out in some midwest states though, used to be in Iowa midgrade could be e15/20

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                      • #12
                        Ethanol is also harder on gaskets and over time dries them out faster than ethanol free gasoline. You could argue that higher octane burns hotter and therefore keeps the engine "cleaner". Probably only relevant if you have the boat for a long time.
                        2000 MC SportStar
                        2017 SQ5
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                        • #13
                          I don't run it because I have an LQ9 that wants 93 octane.[/QUOTE]

                          Are you able to find 93 octane gas, or do you use an octane booster?

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                          • #14
                            Originally posted by Torstenlaw View Post
                            Ethanol is also harder on gaskets and over time dries them out faster than ethanol free gasoline. You could argue that higher octane burns hotter and therefore keeps the engine "cleaner". Probably only relevant if you have the boat for a long time.
                            Pretty much every engine made from 2000 on is compatible with E10 fuel. There won't be gasket or O-ring issues on these engines.

                            Octane is the fuel's propensity to self-detonate when compressed. 93 doesn't burn hotter or cleaner than 87, it can just withstand a higher compression ratio without knocking.

                            Seriously, there's no benefit to running higher octane fuel than what the manufacturer recommends. I'm a petroleum chemist specializing in octane. I know the chemical makeup of these fuels. I see the lab results on a daily basis. Premium ain't cleaner or better in any way except when it comes to compression.

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                            • #15
                              Here in West Michigan we have 87, 89, 93 & 90 ethanol free. My cadillac says use 91

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