Fuel type
 

New owner of 92 Z212 with a 5.7 Merc. It's been 21 years since I bought my first Mariah, so I can't remember what octane of fuel to use. I live in Texas and regular is 87 octane. Is it ok to use 87 with 10% ethanol?

Re: Fuel type
 

In my opinion, the marine environment is a harsh place for an engine. Give it every advantage and don't use Ethanol. The alcohol will attract moisture (water) into the fuel system. Real gas is a little more expensive but worth it to me. I run 91 octane in my 95 5.7 mercruiser. Not sure it really helps performance but it makes it seem like it goes faster:)

Re: Fuel type
 

Some areas your stuck using fuel with ethanol fuel..in NJ I haven't found any area that is ethanol...i personally put 93 into my 4.3 Yamaha usually with a can of seafoam

Re: Fuel type
 

Thanks!
I have located a couple of stations locally that have no ethanol fuel. I'll probably use mid-grade or higher.

Re: Fuel type
 

I think Mercury says 87 Octane (91 RON) without ethanol but if I run the lower grade on my little 3.0 it will diesel (run on when shut off). That tells me the compression is just high enough that depending on ignition advance there's a chances of detonation so I run Premium only. Small price to avoid potential engine damage and some places the only alcohol FREE fuel you can get is Premium anyway. I have to run the same fuel in one of my old cars also.

Edit: left out the word FREE

Re: Fuel type
 

Also, be aware of pumps that have 1 nozzle for all three grades. Tests have shown that there can be up to 5 gallons of 87 octane with 10% ethanol left in the hose and pipes before you actually get the 91 non-ethy. I usually will select the premium and pump about 5 gal into a gas can then start filling my boat. (You could also pump it into your truck.....I have a Duramax diesel so that wouldn’t go over so well for me)

Re: Fuel type
 

I think they have an additive for that😊

Re: Fuel type
 

If I haven't used my boat in a while or first time I use it in the season I always put premium in it. So it cleans out some of the gunk that may still be in the motor. From there on out I just put regular in

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Re: Fuel type
 

Any boat old or new should run 100% gasoline. NO ethanol. Marine pump gas is this way for good reason. Worth the extra money per gallon for any boat. Most ethanol free gas is 90 octane. Should be plenty unless you have high HP motor or compression.