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Octane Requirements 377 Scorpion

Old 07-22-2010, 05:22 PM
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Default Octane Requirements 377 Scorpion

I've recently bought a -04 292 Fastech with the 377 Scorpion setup.

The specification says fuel requirement is 92 octane.
I wasn't read up on the fuel classings, and since 95 octane is regular pump gas in Sweden, I thought that would be sufficient.

I just stumbled upon the info though that US and Sweden use different rating systems, and found that my 95 otcane (RON) is actually 90-91 octane (R+M)/2.

Can I continue to run on this fuel without risking damaging the engines? There are 94 octane (R+M)/2 in every gas station on land, but I've never seen it at the sea stations.

Last edited by Berglund; 07-22-2010 at 05:32 PM.
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Old 07-22-2010, 09:45 PM
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You should be OK to run 90-91 octane. If in doubt, try some octane boost.
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Old 07-23-2010, 06:00 AM
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From Statoil gas specification sheets in Denmark:

92 octane RON (Europe) is 83 octane MON corresponding to 87.5 octane PON (USA)
95 octane RON (Europe) is 85 octane MON corresponding to 90 octane PON (USA)
98 octane RON (Europe) is 87.5 octane MON corresponding to 92.75 octane PON (USA)

I personally run Shell V power which is 99 octane RON and I forgot the MON rating. But I can remember having asked Shell and they said that the MON rating of their 98 and 99 gas is the same.

Mercury Racing says on the sticker on the top of the Scorpion engines to use 92 octane PON or 98 octane RON. However they had provided a sticker with my engines that says to use a minimum of 91 octane PON, but no RON rating.

Can you use 95 octane RON which is 90 octane PON safely ? I don't know.

As I said I try to only use the Shell V Power fuel and then if I am far away from home and need to refuel, I will add some 95 octane RON fuel, which will lower the overall octane rating of the fuel in the tank, and then I will not push the engines too hard on the return trip. Upon my return I will fill up with 99 octane Shell V power.

Regarding octane boosters you really need to seek confirmation how much the product does to the octane rating.

Last edited by Phazar454Mag; 07-23-2010 at 06:15 AM.
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Old 07-23-2010, 06:13 AM
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See here: http://www.offshoreonly.com/forums/f...questions.html

and

http://www.offshoreonly.com/forums/f...ne-600s-2.html
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Old 07-23-2010, 07:13 PM
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Thanks for your responses.

Perhaps I could make a mobile barrel for towing, to fill up V-Power in town. I pass it on my way to my boat anyway so it shouldn't be too big of a problem.

I've run approx 2 full tanks of 95 RON fuel since I've got the boat, and perhaps a total of 10-15 minutes of WOT. Not more at least.

Could the engines have taken damage? I've actually noticed that top end seemed a bit slower directly after my first fillup. I guess it doesn't necessarily have to mean that the engines has worn, but perhaps only a lack of performance that will come back once I start running high octane fule again. My first guess was that it was due to the hull getting a bit heavier soaking up water since I store my boat in the water. (fresh water lake)

What's your thoughts on this?

Last edited by Berglund; 07-23-2010 at 07:32 PM.
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Old 07-26-2010, 04:35 PM
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I just called Mercury Racing Tech Support.

They said that I should "probably" don't have to worry running the 90-91 octane (R+M)/2 that I've been using so far, since it's so close to the rated 92. The knocking sensor might adjust ignition though, making me loose a bit power while running. I will be fun to try running higher octane for the first time, so see if there is any noticable difference.

Regarding nocking, I actually have a hard time thinking it can be a big problem with only 9,0:1 in compression ratio.
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Old 07-27-2010, 01:33 PM
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Originally Posted by Berglund
I just called Mercury Racing Tech Support.

They said that I should "probably" don't have to worry running the 90-91 octane (R+M)/2 that I've been using so far, since it's so close to the rated 92. The knocking sensor might adjust ignition though, making me loose a bit power while running. I will be fun to try running higher octane for the first time, so see if there is any noticable difference.

Regarding nocking, I actually have a hard time thinking it can be a big problem with only 9,0:1 in compression ratio.
I don't know what you mean by 90-91 octane ?

Do you mean 90.5 ?

Have you found any evidense of 95 RON gas with a spec of 87 MON giving 91 PON in Sweden ?
I doubt it, since 87 MON is close to the 87.5 MON rating used for 98 and 99 RON gas.
Or is some 95 RON fuel in Sweden actually 96 RON with a MON rating of 86 giving 91 PON ?

In Denmark I have only seen 95 RON octane gas as having 85 MON octane, which is 90 PON. At least that is the information I have from Statoil and Shell in Denmark. It could be different in Sweden though.

Statoils Danish spec sheet can be read here: http://www.statoil.dk/file_archive/f...b_21052010.pdf

My Scorpion engines are manufactured in October 2004 or later. Together with the engines came special stickers and information that the engines are approved for minimum 91 PON (even though it says 92 PON on the top of the engines). The question is if earlier years of Scorpion engines are also approved for 91 ?

I can tell you that the knock sensors are used. Already around 4000-4500 RPM the ECM expects knock inputs based on my experience. If they don't get knock input an alarm sounds. Why do I know ? I forgot to connect the knock sensor wire on one engine after having fixed a minor leak with my Superflush flushing system, that is why I found out about it.

I think you should have asked Mercury Racing Tech support if 95 RON or 90 PON fuel can be used. If it can it would be great news.

Last edited by Phazar454Mag; 07-27-2010 at 02:58 PM.
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Old 07-28-2010, 08:57 AM
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I'm not read up on this topic nearly as much as you.

I just found some fuel comparisation tables on wikipedia where it says that 95 RON equals 90-91 PON.

http://en.wikipedia.org/wiki/Octane_rating

Perhaps I should call them again for a bit more thought through response.

When i bought my boat it had a 3/4 of US fuel, probably 92 PON. I filled it up to full with 95 RON Swedish pump fuel. At my first test i ran 74,8mph at 5200-5300rpm with full tank and two passengers.

Since then, running 100% 95 RON I haven't been able to get it above 73mph and 5000rpm. It might be, as I mentioned before, that the hull has sucked up quite much water and therfore is heavier. But it is more probable that the engines are constantly adjusting ignition against nocking and therefore limiting performance. I haven't run it yet under 1/2 tank and less than 2 passengers though.

What do you think?

Last edited by Berglund; 07-28-2010 at 09:01 AM.
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Old 07-28-2010, 03:35 PM
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Originally Posted by Berglund
I'm not read up on this topic nearly as much as you.

I just found some fuel comparisation tables on wikipedia where it says that 95 RON equals 90-91 PON.

http://en.wikipedia.org/wiki/Octane_rating

Perhaps I should call them again for a bit more thought through response.

When i bought my boat it had a 3/4 of US fuel, probably 92 PON. I filled it up to full with 95 RON Swedish pump fuel. At my first test i ran 74,8mph at 5200-5300rpm with full tank and two passengers.

Since then, running 100% 95 RON I haven't been able to get it above 73mph and 5000rpm. It might be, as I mentioned before, that the hull has sucked up quite much water and therfore is heavier. But it is more probable that the engines are constantly adjusting ignition against nocking and therefore limiting performance. I haven't run it yet under 1/2 tank and less than 2 passengers though.

What do you think?
Hi David

I have no knowledge ragarding the fuel issue, but I have question regarding that the hull has sucked up water, is that normal on a sound fiberglass hull??
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Old 07-28-2010, 04:06 PM
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Originally Posted by Berglund
Since then, running 100% 95 RON I haven't been able to get it above 73mph and 5000rpm. It might be, as I mentioned before, that the hull has sucked up quite much water and therfore is heavier. But it is more probable that the engines are constantly adjusting ignition against nocking and therefore limiting performance. I haven't run it yet under 1/2 tank and less than 2 passengers though.

What do you think?
I don't know to be honest. Try the higher octane fuel to see if it makes a difference. If it doesn't then I guess it is something else like higher temperature, or other parameters. I don't know how much weight the hull gains without protective primer.

What props are you using ?
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