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Old 04-25-2017, 09:18 PM
jkcTN jkcTN is offline
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Join Date: May 2012
Boat: Current: 2016 X46 7.4L, Previous: 2007 X15 MCX350
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ilmor 7.4L

Anyone run this engine with 87 octane? According to ilmor it is rated for 87 but I've heard from other sources that I should run high test.. The closest marina to me (literally 5 minute idle) only has 100% gas 87.... there is a marina (15 minute boat ride) away that does have high test... I'm just wondering if it's worth the extra drive and cost of high test to run that grade in the boat.

Bottom line I'm looking for people that have real world comparisons in running both grades in the ilmor 7.4 power plant.
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Old 04-25-2017, 10:34 PM
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lashburn1 lashburn1 is offline
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Boat: 2016 G21 Coastal
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87 is fine. Use quality fuel as much as possible
Shell/Chevron/Texaco
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2016 G21 Coastal
2014 X46 GEN2 7.4
2014 X30 GEN2 5.7
2006 VRS200 5.7
2013 X30 GEN2 6.2
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  #3  
Old 04-25-2017, 10:35 PM
sdfoiler sdfoiler is offline
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Join Date: Jun 2015
Boat: 2013 X-Star - 7.4 Ilmor
Location: midwest
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Run 87 anytime I can in my 7.4 - If it's good enough for the Ilmor engineers, it's good enough for me.
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Old 04-26-2017, 03:08 PM
IBR IBR is offline
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I run ethanol free 87 oct. in mine about 90% of the time. I haven't noticed any difference when running 93 octane.
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  #5  
Old 04-26-2017, 03:29 PM
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kscrib kscrib is offline
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I only buy premium gas. Not because of the octane, but because in MO most fuel is ethanol based, but some gas stations sell premium (91 - 93 octane) that is ethanol free.

Is anyone else afraid of ethanol? I am afraid it will pull moisture into the fuel system and cause more expensive repairs than I am paying for the higher priced gas.

If it matters I have a 2015 with 6.2L
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Old 04-26-2017, 03:32 PM
hunter991 hunter991 is offline
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Quote:
Originally Posted by kscrib View Post
I only buy premium gas. Not because of the octane, but because in MO most fuel is ethanol based, but some gas stations sell premium (91 - 93 octane) that is ethanol free.

Is anyone else afraid of ethanol? I am afraid it will pull moisture into the fuel system and cause more expensive repairs than I am paying for the higher priced gas.

If it matters I have a 2015 with 6.2L
I am.. i hate the stuff. i put 91 octane only in my 5.7. i won't use ethanol in my snowmobiles, boats, atv's, hell even my lawn mower if i don't have too.

Boats can sit for weeks and it leads to phase separation. If you have too, i add some marine stabil to counter act it. But eth blended fuels are no good for items that sit more than 30 days.
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  #7  
Old 04-26-2017, 03:44 PM
ryancassidy ryancassidy is online now
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I was reading (and I can't recall where) and my dealer also recommends just the regular 87 for all the new MC ilmore engines. I used to use only Non-Ethanol fuel previously in my higher strung engines (ie Yamaha jet skiis) but for right now I'm using regular 87 with Marine Stabil.

all my lawn equipment runs Non-ethanol, but it's older and just not built for it.
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  #8  
Old 04-26-2017, 05:04 PM
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clrussell clrussell is online now
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Quote:
Originally Posted by kscrib View Post
I only buy premium gas. Not because of the octane, but because in MO most fuel is ethanol based, but some gas stations sell premium (91 - 93 octane) that is ethanol free.

Is anyone else afraid of ethanol? I am afraid it will pull moisture into the fuel system and cause more expensive repairs than I am paying for the higher priced gas.

If it matters I have a 2015 with 6.2L
I only run premium in everything.. lawnmower, Prius, boat..

If that tells you anything
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  #9  
Old 04-26-2017, 05:09 PM
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Mastercraftdave Mastercraftdave is online now
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Boat: 2015 X23 SS 6.2L
Location: New Orleans, LA
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Quote:
Originally Posted by clrussell View Post
I only run premium in everything.. lawnmower, Prius, boat..

If that tells you anything
Im with you. I only run premium in my X23. The manual even says that 93 octane is best for the engine. See below


"Poor-quality or old fuels can cause problems such as loss of performance,
rough idling, hard starting and hesitation. If the engine experiences any of
these symptoms, first try another brand of gasoline and/or replace the old
gasoline with fresh gasoline."

I have the 6.2L in my truck and GM recommends 93 and states that 87 octane may reduce engine performance.
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  #10  
Old 04-26-2017, 05:19 PM
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Snipe Snipe is offline
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I will use ONLY non ethanol. Had issues earlier. Even though It's only a 5.7
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