Which is needed for merc 525 blower motor?

ttt

all merc engines are made to run on 87. So you do not need the highest grade but do buy it from a store with a hi volume of sales so you do not buy old gas, And also try to avoide buying gas while on the water at the fuel dock marinas more then most of them have water or dirt to sale you at a higher price.

Per the Merc service, the 525SC requires minimum 92 octane fuel.

Same for 600SC and 800SC.



Darrell.

BTW my motors started life as gen VI SC600's, and now making 800. I run 91 octane in them( this is all that is available in CA.). I have had zero problems with running them this way.





Darrell.

Sorry about my first post after doing some home work DMOORE is right 92, I was just going off my bad memmory from service school on standerd stock engines and remembered them saying all merc engines run on 87 and I was thinking the same on the [HP] stuff also.

Where I boat the fuel sold on land is a blend. So, we are forced to buy fuel only for marine applications.

92 octane as stated is required for the 525SC per Merc. Its right on the Flame arrestor. I would run teh 93 to be safe. Also, then if you have to add some 91 or 89 to get home in a pinch, it will mix with the 93.
I have read about people runnning as low as 89 octane in them. I always ran 92 or 93 octane in mine.