What Gas do you use?

[peytonvp]

I have been wondering this for a while so figured that I would go ahead and ask. For those of you with the older indmar 5.7s and 6.0s, do you use 89 octane and 91 octane respectively as per the manual. I have always done stuff by the book and have been debating just running 87 in the boat. I can't really see the harm in running 87 but I figured that I would get some other opinions on the matter.

[TolCarMan]

I run 87/88 octane (mid grade in UT) in my 5.7 MCX and have never had an issue.

[robadele]

89 plus stabil marine ethanol treatment. I don't use that much gas over a summer with only 40-50 hours, so why not use what is recommended.

[jtryon]

87 and never an issue.

[3event]

I've got the Predator/RTP power plant. 89 was recommended, and used 89 since day one in 2002. I can't remember the last time I asked a dealer just to check if anything had changed, but when I last did - the answer was nope - stick with it.

[Double D]

Always ran 93 Octane in my boats until recently the station close to me now has non-ethanol Rec90.

John Horton on Ball of Spray did an experiment this year on skiing behind the same boat with different octanes. See for yourself.. https://ballofspray.com/forum#/discu...tane-theory/p1

[Ironhorse]

I run 91 Octane in my boats, sleds, quads, pwc's and car, but run 87 in my truck.

[JimN]

I run 91 Octane in my boats, sleds, quads, pwc's and car, but run 87 in my truck.

Why 91, unless they call for it? Do they sit for long periods? What does your truck actually need?

[JimN]

I have been wondering this for a while so figured that I would go ahead and ask. For those of you with the older indmar 5.7s and 6.0s, do you use 89 octane and 91 octane respectively as per the manual. I have always done stuff by the book and have been debating just running 87 in the boat. I can't really see the harm in running 87 but I figured that I would get some other opinions on the matter.

Lower octane burns faster, which can cause detonation (knock or pinging) in hot, dry air and hard acceleration/load. If it calls for 89, it's better to go high than low.

[Double D]

Lower octane burns faster, which can cause detonation (knock or pinging) in hot, dry air and hard acceleration/load. If it calls for 89, it's better to go high than low.

Totally agree here and was really noticeable when I was running an S-10 with a 4 cylinder. Anything below a 91 that engine was knocking and pinging like crazy. Hated it!

[Wheelin98TJ]

I have an '05 Indmar 6.0 LQ9 and it calls for 93 octane.

I've always used 93, so can't say if it runs ok on less than that.

[Ironhorse]

Why 91, unless they call for it? Do they sit for long periods? What does your truck actually need?

The SXR's have built engines and need it, the car and sleds call for it, so its easier to fill 12 jerry cans for the lake with the same fuel so running out of one or the other is never an issue. The truck calls for 87 and gets the most use, so that's an easy call.

[JohnE]

Lots of threads on this. Here is one. Jim's been educating us for years. https://teamtalk.mastercraft.com/sho...ghlight=octane

[peytonvp]

Lower octane burns faster, which can cause detonation (knock or pinging) in hot, dry air and hard acceleration/load. If it calls for 89, it's better to go high than low.

That has always been my thoughts behind using the right octane. I know that modern fuel injection systems can retard timing so it is not as much of an issue but I know it is always better to be safe than sorry. The funny thing is my friend has 4 2007 Seadoo RXT, which are the supercharged skis, and he has run regular 87 octane since day one and he has over 300 hours on each ski. Skis call for premium but I would say he has had pretty good luck. That said I am not as brave and always run premium in my turbo skis.

[rbuss4]

Premium (mostly 91 here in WI) with no ethanol ALWAYS. My mastercraft is my second biggest investment(after real estate) and a couple extra bucks every fill up is worth it to me. Small engines (jet skis, snowmobiles, lawn tractor, chain saws, etc.) all get non ethanol premium as well. If we had mid-grade (89 octane) with no ethanol; I would use that in everything but the boat.