What's are the effects of Octane?

[Allyfishing]

I was reading a post on the forum here and now can't find it but this link was posted to show the differences between Mercury performance engines:

http://www.sandersonpropeller.com/table1.html

What I did notice was the octane recommendation for the Promax 225X (93) compared to the ProMax 225 SS and 225 Offshore (89). Is a 1996 ProMax 225 the same as the SS and the Offshore and if so does it fall under the same octane rating of 87??

Reason I ask is I was told to use 93 octane in my 1996 225 PM and I read articles on using too much octane is just as bad as using too little in a performance motor.

Any input on the subject?? What octane should be used in a '96 225 PM and what are the effects of using different octanes?
Thanks
Craig

 

[ROBERT CROSS]

Craig,

Both my owner's manual and service,(09-840541), manual specify 91, I'll stick with that and Aces IV at every fill.

Bob
:beer:

 

[xb03]

Im pretty sure that the 89 rating was raised, because of cheap gas and the lean ecu problem/fix. IMO 93 is not too much for these motors, and it surely won't hurt anything. If I remember correctly the A17 was the lean running ecu.

 

[h2oskiier30]

Using "too much" octane is in no way just as bad as using too little. Using too little will get you a hefty repair bill with melted pistons. Using too much octane will simply rob you of a very small amount of performance, but will be perfectly safe for your engine.

 

[resqu-u]

The 89 rating is the min. I try to run 93 w/o ethanol. Luckily I have a station right outside the base that still carry's REAL BP gas and I run sea foam every other tank. I've ran 89 without any notable difference in the boat. Our 2011 maxima has a 93 min, I can tell a difference in performance with fuel. The wife filled it up with regular one time and it ran like crap! Makes me wish I'd bought a Honda with Gas going past 4.00 a gallon now...

 

[whipper]

All correct info as far as I was ever told also. I dont know a whole lot about the whys but I do know the does and donts. Mines also a 96. i run 91 min always and no issues. If your above sea level you can get away with less Octain also. Thats why I use 91 Im always above 1000ft. Ive used 94 before and never noticed a differance but have found 91 to be used with no issues running my 225 over 7000 rpm all the time premixed.

What Robert said is the best idea if ya ask me for these motors. Just get some Aces and run it with every fill and you will never have to worry about 91 oct fuel or worry if the gas isnt as marked. The peace of mind knowing your covered is worth it for Aces. Todd sells it and uses it along with lots of other Allison owners and high performance boaters with our motors.

 

[suicidealli]

I would run the best pump gas you can get in any outboard engine...
Set you engine up correctly to run on it, with some room for poor gas just in case! Aces is always a good idea. Jmo

Roy

 

[whipper]

I would run the best pump gas you can get in any outboard engine...
Set you engine up correctly to run on it, with some room for poor gas just in case! Aces is always a good idea. Jmo

Roy

Roy what do you mean by set your motor to run on pump gas? What type of things do you do for that? Im guessing run a richer ecu as mentioned about the A17 running lean perhaps lower pitch props, but what are some other things one can do?

 

[Allyfishing]

Thanks for the replies. I always use 93 octane and will continue to do so. I just remembered reading somewhere that too much octane on stock compression heads will cause too slow of a burn and not completely

 

[h2oskiier30]

Roy what do you mean by set your motor to run on pump gas?

I would guess that he mostly means getting your heads cut to a compression that you can safely run with the gas available in your area...at the same time maximizing performance.

 

[h2oskiier30]

I just remembered reading somewhere that too much octane on stock compression heads will cause too slow of a burn and not completely

That is correct, and that's not anything that is going to harm your engine.

 

[patches]

Using "too much" octane is in no way just as bad as using too little. Using too little will get you a hefty repair bill with melted pistons. Using too much octane will simply rob you of a very small amount of performance, but will be perfectly safe for your engine.

Bingo!!!

 

[suicidealli]

I would guess that he mostly means getting your heads cut to a compression that you can safely run with the gas available in your area...at the same time maximizing performance.

That is exactly what I mean!!!!!
Running higher octane than you need won't hurt you, but you should take advantage of the oct.. If you are running more oct than you need, there are other things, like timing, fuel delivery, "curve" to make a great tuned engine...


Roy

 

[whipper]

I see. Im running 91 with 33cc heads. A fairly lean fuel curved acu and timming set to 25. Mix 40-1. i do find with 91 and aces an inprovment at 2200ft above sea level. Sure would like to see what 93 and aces at sea level would be like with the added HP and Comp.

 

[Allyfishing]

That is correct, and that's not anything that is going to harm your engine.

Ok....that's good. No harm. So what happens to the excess if it is not burned completely? Will it carbon up the engine? So there's no sense using something like ACES, for example, if 93 octane is available on say 135-138 compression heads on a basically stock 225 ProMax?

 

[catfish123]

Hi Craig........I believe you are just fine at that compression level with 93 octane gas. According to TV last night........regular gas should be $5.00/gallon this summer. If that's true, 93 octane plus the 2 cycle oil will put us to $6.00/gallon. Unecessary additives will just further put a drain on our bank accounts. I'm running 152 compression with high test gas without Aces and everything is fine like that. I believe the Aces only begins to be a benefit at higher compression numbers.

 

[Allyfishing]

Yup, that's what I figured Bob!! I was listening to FOX news yesterday about the oil prices and the eventual gas hikes in the near future and it really pisses me off how we the people have to suffer for the governments mishandling of our current economy!!!

 

[catfish123]

Yep........I'm afraid my trips to the lake this year may be limited by my inability to come up with the money needed to do it............or.......I'll be doing a WHOLE LOT MORE FISHING. I have always liked Seafoam and I continue to use it in every tank of gas I run. Just bought a 24 can case of it on Ebay. I would hate to have to do it to fund my boating this year........but I may just have to sell the Sportmaster that I picked up from Sanderson's a few months ago...............LOL

 

[TBuck2003]

Craig from a compression point of view, you do not need ACES to protect your motor. But keep in mind it does a lot more than that. Let me run through the benefits with high compression being omitted.

1. Fuel pump lubricator

2. Fuel injector cleaner

3. Carbon remover

4. Upper cylinder lubricant... This to me is worth it by itself.

5.Fuel stabilizer

6. Battles Ethanol up to E-20

From these benefits there is no need to run anything else. From my situation my boat sits up to 6 months a yr. I have never added anything to my tank since I have been running ACES and have had nothing but great results. I can pull my boat out first time in the spring and run it like I did when I put it away. My 260 is now going on yr. 6 (Knock on wood) and that entails wake boarding,skiing, and 8500-9000 passes. This would be like 3-4 yrs. worth of use if I lived in a 12 month boating environment. I have never put in any product in my tank other than ACES. This is just an explanation to Craig regarding other benefits.


TBuck

 

[Allyfishing]

Thanks for the explanation Todd. I admit that when I first got my ProMax I used all sorts of stuff all at the same time so I was basically overdosing my engine with too much additives all with good intentions to combat ethanol and wanting my engine to live a long time.