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Fuel for the 7.4 Merc
Posted: Fri Apr 27, 2018 10:39 pm
by Protip
Our boating season is in full swing now. Going out for a full day again on Sunday and am going to have to fill up for the first time in the new (to me) boat. I don't need to run premium in it right? Will be getting marina gas since my trailer deal fell through so it should all be no ethanol.
Re: Fuel for the 7.4 Merc
Posted: Fri Apr 27, 2018 11:46 pm
by cmattj
Protip wrote: Fri Apr 27, 2018 10:39 pm
Our boating season is in full swing now. Going out for a full day again on Sunday and am going to have to fill up for the first time in the new (to me) boat. I don't need to run premium in it right? Will be getting marina gas since my trailer deal fell through so it should all be no ethanol.
87 is fine. E10 is common so no worries there either. Every state is different.
So go fill her up.. don't ask how much.. just sign the paper and tell the person you don't need a receipt! Have fun
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 12:24 am
by Ytmsn
Matt... Ethanol is $#!+. Jus sayin....
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 5:45 am
by thunder550
Yep 87 is good.
As long as condensation isn't allowed to collect inside the tank, is E10 really that bad either?
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:30 am
by cmattj
Ytmsn wrote: Sat Apr 28, 2018 12:24 am
Matt... Ethanol is $#!+. Jus sayin....
I said its common.. never said it wasn't mmmmm How did you Curse legally?? OH thats right..... S#!T
were going to Detention for that one.
thunder550 wrote: Sat Apr 28, 2018 5:45 am
Yep 87 is good.
As long as condensation isn't allowed to collect inside the tank, is E10 really that bad either?
I don't think 10% is that bad if you keep using it and burning through it.
The Problem is that E10 is a water sponge as you know. And open fuel systems like Boats are awful for that.(they pull moisture even with no Ethanol in the gas when they just sit around) .
So company's make additives to offset that . Or if we just let set it for a few months.... turns to s#!t. (that was legal cursing)
Remember how you where changing fuel filters a lot. ? should I pick up a mid season surge at steady speed first thing id try is replace the fuel filter, and I start with a fresh Fuel filter every year anyway as im sure most everyone does.
It could be worse.... Flex-fuel or E85 requirements next?? then what

Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:48 am
by Big Block Power
Matt your awesome. Detention you Yt and that T5554554555500000 guy.
Most marinas run premium. So just watch what octane they use. Not that it matters just saying that why you pay more also.
E10 doesn't go in my boat.It's easy for me to get it without it here. We freeze our real gas here in the north plenty of it. Ethanol/Alcohol let's face it. It's a cleaner and a non lubricator so after awhile depending how old your system is it is not set up for ethanol and may fail early because of that. You also lose performance from it unless your engine is set up to race with it line Matt likes too.
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:51 am
by Ytmsn
Dang BB. You're in full bloom today. What scares me is I almost understood most of that post
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:52 am
by Tuscany
Ethanol is corrosive.
We all run it every day in our vehicles, which is fine. Goes in, we burn it, and fill up again consistently. But ethanol in a vehicle that may sit for extended amounts of time can lead to trouble.
Personally, I only use ethanol free 91 in my recreational engines.
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:52 am
by Big Block Power
Ytmsn wrote: Sat Apr 28, 2018 7:51 am
Dang BB. You're in full bloom today. What scares me is I almost understood most of that post
Yep and I just woke up.I showered first. Maybe that helped. Off to my work to help my kid buy a new Ram

Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:53 am
by Big Block Power
Tuscany wrote: Sat Apr 28, 2018 7:52 am
Ethanol is corrosive.
We all run it every day in our vehicles, which is fine. Goes in, we burn it, and fill up again consistently. But ethanol is a vehicle that can sit for extended amounts of time can lead to trouble.
Personally, I only use ethanol free 91 in my recreational engines.
Yep same here. Snow blower and mower don't get ethanol gas.
Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 7:59 am
by cmattj
Big Block Power wrote: Sat Apr 28, 2018 7:53 am
Tuscany wrote: Sat Apr 28, 2018 7:52 am
Ethanol is corrosive.
We all run it every day in our vehicles, which is fine. Goes in, we burn it, and fill up again consistently. But ethanol is a vehicle that can sit for extended amounts of time can lead to trouble.
Personally, I only use ethanol free 91 in my recreational engines.
Yep same here. Snow blower and mower don't get ethanol gas.
+1. 91 here too.... Some Boat technology sees ping and knock and will reduce the timing automatically during that key cycle..

Who wants that hahah
Whats a snow blower?

Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 9:06 am
by AsLan7
Protip wrote: Fri Apr 27, 2018 10:39 pm
Our boating season is in full swing now. Going out for a full day again on Sunday and am going to have to fill up for the first time in the new (to me) boat. I don't need to run premium in it right? Will be getting marina gas since my trailer deal fell through so it should all be no ethanol.
.
Like the others mentioned above, that's correct protip.
From page 1B-14 of the 1999 Mercruiser 7.4L service manual:
https://d3gqux9sl0z33u.cloudfront.net/A ... _litre.pdf
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Re: Fuel for the 7.4 Merc
Posted: Sat Apr 28, 2018 2:28 pm
by Protip
Great, thanks guys.