F14A,

Another dumb question...

Again, since I don't need triple digit octane, I can actually get what I need from the pump. But, as I stated, most pumps don't have 91, and the 93 seems to suet up the transom something fierce. Could a guy get away with pumping equal amounts of 89 and 93, and expect 91 octane as a result? Obviously, I can do the math, but does the chemistry work that way?

Thanks. Brad.
Model Machine and Precision LLC
(937)545-8991

It will be more cost effective to get your fuel at the pump.
Yes, equal parts of 89 and 93 will get you 91 octane.

And......please stop posting your business info in your posts unless you wish to purchase a Commercial Membership.

Octane has nothing to do with soot on your transom especially a difference of 2 points. YOu got something else going on . Soot means you`re running rich.
Run as much octane as you can, octane is resistance to detonation, that`s it. It doesnt burn slower or faster like the old wives tales would have you believe.
If your engine is set up to run 89 octane and you put in 116 you wont lose or gain power. There`s an entire episode on this (engine masters).

Boosted you need to see what your final compression ratio is and that determines if you need more octane then pup gas can provide.
There`s more to it but here`s a general rule chart:(bosted)

https://goodvibesracing.com/Compression_Ratio.htm

as an example if my engine is 8.0:1 and I`m running 10 psi I should be running some boostane because pump gas is not going to cut it .

Dan most 500 efi and 525 boats have noticeably more soot on the transom with 93 than 89, and many have tested to run a tick slower with 93. That said, Mercury has notoriously rich tunes.

Dan just ordered two 5 gallon buckets Boostane Prof. thru Boostane. Delivered $599.99. Bought 5 gallons through Amazon a few weeks ago and it was $425.99 delivered. So for $175 I got an additional 5 gallons. Super deal! Took me a few times to get the BOGO code right. Code has a zero at end. I tried to make it an O. Thanks for the heads up!

That`s a great deal! yes the last 2 are numbers fifty (50)
I bought 12 cans of the marine for $277.
Their email said it was only for black friday deal so I`m glad it still works . I may order more

That`s interesting. Any idea why octane would cause sooting ?Does not compute to me.

The outcome of this episode where they dynoed the same engine on 87 thru 116octane race fuel and optimized timing and fuel... it made almost no difference in power .

https://www.facebook.com/watch/?v=744265356291138

Typically factory EFI.
Many set ups (as a whole, not just boats) first time over , say, 60% throttle , each run period, will do quick knock sensor test. Will go to preprogrammed timing # where it shoukd knock. If it doesn’t the computer will run at a lower timing table thinking the knock sensor system isn’t working right. Some efi programs will also add touch more fuel.

Thus why you typically don’t see a carb or aftermarket efi do this, with just octane change.

Oh that is interesting but makes sense !!

On the 500EFI it normally comes out to about 5hp on the dyno, not that you would notice that in the boat.