Octane levels

[nexis420]

Hi this may sound like a stupid question but is it ok to run high octane fuels in your seadoo.. i have a 07' GTI SE and last summer i always used 87 octane which is what the manual says.. gas being as expensive as it was last summer too i suppose, however i would like to run higher octane this year or even every now and again.. is it ok to use the ultra 94 octane or 91 octane? also when hooking up a battery you connect red first and black second? thanks for your time

 

[timmyboy76]

hook'n battery, i hook black then red..? for gas, 91 will work, hav'n 94 pump, might need to run hotter plug?, but ok on the 91.

 

[kustomkarl]

The seadoo engines are designed to run on 87 octane. Unless you have done some modes, you just wasting you money because if the engine doesn't need it it just goes out the exhaust pipe. If you raise the compression or change the timing than you will need higher octane to keep it from pinging. Only the Super Charged engines need 91 or better octane. You could run 105 octane and it won't run any better...just cost you more.

Karl

 

[glenwhitt]

worse with higher octane

Is it true that with the hotter point of ignition fuel in a lower compression engine that it can actualy not run as good? Has to be true. Read it on the web

 

[seadoosnipe]

yes....

Yes, your correct. This was discussed a year or so ago in the forum. The higher octane in a lower compression engine is not efficient. You need to run what the recommended requirement is.

If you have no choice but to run E85 or 90, then you need to use Stabil in your fuel. They have a mix out now just for helping to keep the moisture from collecting in your fuel because of the alcohol.......:cheers:

 

[peridot0283]

The seadoo engines are designed to run on 87 octane. Unless you have done some modes, you just wasting you money because if the engine doesn't need it it just goes out the exhaust pipe. If you raise the compression or change the timing than you will need higher octane to keep it from pinging. Only the Super Charged engines need 91 or better octane. You could run 105 octane and it won't run any better...just cost you more.

Karl

I have a '00 GTX RFI, it seems to run better with 90 or above, on the 87 gas it bogs and even seems to not want to start easily, any idea's why?

 

[peridot0283]

I have a '00 GTX RFI, it seems to run better with 90 or above, on the 87 gas it bogs and even seems to not want to start easily, any idea's why?

Also the machine is completely OEM, nothing modified.

 

[kcr357]

The octane rating of fuel is a measure of how much octane is present in the fuel. Octane is a chemical in fuel that is very resistant to detonation and is slow burning. Lower octane fuel is faster burning than high octane fuel, and actually should provide better performance than high oct if compression ratios allow it to be used. High octane fuel is used to keep high comp ratio engines from detonating when a low octane/more volatile fuel would prematurly combust from the heat and pressure. So no, high oct fuel will not hurt you motor, just your wallet. I have no Idea why high octane runs better on certain machines. It shouldnt according to all conventional knowledge, but my 85 trike ran awesome on BP94. Cant figure out why...

 

[kcr357]

Unless there is a knock sensor that retards the timing when the engine detonates, but I dont think ur ski has that

 

[kcr357]

I have a '00 GTX RFI, it seems to run better with 90 or above, on the 87 gas it bogs and even seems to not want to start easily, any idea's why?

Ru using one brand of fuel> There low oct might be crap. Try a different station. If ur in the middle of nowhere, all the stations might have the same gas....

 

[aklim]

Maybe it runs better on higher octane because it needs it. Could be that something is causing detonation which is why it runs better on higher octane stuff.

 

[ted-hurst]

I thought it was just me but my 1999 GTX RFI runs better also on Chevron 93octane (100% gas). I just filled up yesterday with Citgo 87 octane (has up to 10% ethanol) and throttle response wasn't as good and I lost about 200 rpm's off of top end. I don't think the octane level made the difference but I've heard that the ethanol lowers power and you get worse fuel economy. Seadoosnipe is right about adding Stabil (Ethanol Formula) to your fuel, the ethanol can do real bad things to the motor and I put Stabil in everything, generator, mower, boats and ski.

Ted

 

[scooper77515]

Old thread, but still relevant.

I was actually thinking of running a tank of 91 just to see if I notice a difference.

I expect it to be a waste of money, but have no problem with being pleasantly surprised. :cheers:

 

[ted-hurst]

As soon as I run out this gas (ethanol) I'm going back to the Chevron station and fill up with the 87 octane (100% gas) and see if there is a difference between the two.

Ted

 

[scooper77515]

How are you going to determine a significant difference? Hours per tank, seat of pants, or what?

 

[ted-hurst]

When I first got the ski I emptied and cleaned out the fuel tank, and then went to the Chevron dealer filled it and 100% gas, 93 octane. I put it in the water and had a rave valve issue, fixed that and then ran it at Navy Point area. It's a nice little area in Pensacola, pretty straight and protected from the wind. Ran the ski back and forth on the straight away 4-5 times each way and was watching my tach and handheld GPS. I got 6750-6850 rpm's and 49-50 on the GPS (with the Chevron). Then when I refueled with Citgo (up to 10% ethanol) 87 octane, did the same thing with the same weather conditions, but didn't have my GPS, all I could get the rpm's up to was 6550-6650. I plan on going out there again and trying it a few more times so I can get a better average. After I run the Citgo down I'm going to refuel with Chevron and try it again. Again I don't think the octane difference caused to rpm/speed drop but maybe the ethanol did. I've heard and seen some bad things done by ethanol at one of the local boat dealers.

Ted

 

[onebadcav00]

sta-bil marine. its blue. use it.

 

[scooper77515]

Ted-hurst!!! :hurray::hurray::hurray:

I love to see this kind of REAL experimentation. Especially when you try to factor out as many of the other potential issues as you can to verify that one thing works over the other. It is a major hassle and a waste of time (as far as most people are concerned), but I find that wasting my time and a tank of gas is WORTH IT if even 2 or 3 other people read my results and save themselves a hassle later on.

Not sure if you can read this, but I will post a link to a quite expensive and yet VERY informative question that we had on my Maverick forum. The question for years was, "how much easier is it to steer with a power steering setup over a manual setup?" and the answer was always "alot". But that is subjective. So I did torque measurements and then swapped out the power for a manual setup to get REAL numbers, so that the other members could decide if they wanted to do the swap themselves.

http://mmb.maverick.to/showthread.php?t=28363&highlight=power+manual+steering

You guys may not be able to access this site, if not, I will delete it. But I have a reputation for actually running "experiments" and not just saying "I think it feels better..." and I respect that in others even if it is a drain from their pocket book.

 

[05GTXSC]

Run 87 in the 05 SC no issues and don't plan on changing.

 

[ted-hurst]

Thanks scooper77515, I'm a retired Marine and work at a Naval rework facility in Pensacola and love to tinker. Got a 30 Ford Coupe that I spend a lot of time on and this is my first ski and I'm having a blast with it so far. Plus doing this I get to get out of the house more and the kids love it. I've gone through the pump, replaced the driveshaft, impeller, voltage regulator/rectifier, starter and learning alot from everybody on here. And Stabil Ethanol formula is a definite, been to a couple classes and that ethanol is bad stuff especially in boats.

Ted

 

[b15philly]

My 96 GSX runs much better with 93 octane, im not sure if its because of the mods I have but I did a GPS test comparing 87 to 93 octane and found a pretty significant difference. When using 87 octane from a Mobil gas station my ski would run 54 to 56 MPH on the gps using 93 octane from the same Mobil station and running the ski in the same weather conditions I was consistently hitting 60 MPH. Im running a stock head and my compression is 145 in both cylinders:cheers:

 

[scooper77515]

Well, that is about the 5th time I have heard about the negatives of ethanol. I guess I need to buy some of that stuff and add it to the gas.

 

[onebadcav00]

its 10 bucks per bottle. one bottle treats 80 gallons. i got a couple bottles at advanced auto parts. i am sure car quest and others will have it too.