Fuel Question

[Havasu Cig]

According to Merc's site the 300x's require 92 octane. On my 2.5 boat they reccomended that I run AV as opposed to 91/92 pump gas. Does the same apply to the 300x's, and since 91 is the highest you can generally find at the pump is that what most are using?

[TOBTEK]

I was told from the Merc reps, to run AV gas ONLY. Very cheap insurance! The gas out of the pumps are at times oxgenated (sp?) ........damn gas station owners..... :)

[Kilrtoy]

Ok this needs further explaination

[Kilrtoy]

Ok just read the manual and it says 91.....for the 300x's

[TheLurker]

I was told from the Merc reps, to run AV gas ONLY. Very cheap insurance! The gas out of the pumps are at times oxgenated (sp?) ........damn gas station owners..... :)
I’m not posting this to start any griping about gas prices or get personal. I just want clear up an incorrect statement;
Station owners have no say in whether they get oxygenated fuel or not. For that matter refiners don't either.
Oxygenates MTBE, Ethanol etc are federally mandated due to air quality regulations. The logistics of storing, blending, shipping all of these “boutique fuels” for the different metropolitan areas is very costly. This is one of the many reasons you will see the spring price spike and yes profit margins are another.

[HavasuDreamin']

Run av-gas or at least 50/50 av-gas & 91 to guard against detonation and a hole in your piston. All it takes is one bad batch of gas and you can do SERIOUS damage! Why risk it? If it were me, I would run straight av-gas or at the least a 50/50 mix of av-gas and 91 octane. I would also run Klotz KL-333 synthetic or another quality synthetic lube.
Good Luck. :mix:

[Havasu Cig]

Well then AV it is. Damn, I was hoping I could fill at home. :cool:

[TOBTEK]

I’m not posting this to start any griping about gas prices or get personal. I just want clear up an incorrect statement;
Station owners have no say in whether they get oxygenated fuel or not. For that matter refiners don't either.
Oxygenates MTBE, Ethanol etc are federally mandated due to air quality regulations. The logistics of storing, blending, shipping all of these “boutique fuels” for the different metropolitan areas is very costly. This is one of the many reasons you will see the spring price spike and yes profit margins are another.
I ONLY WAS POKING FUN AT HAVASU SIG/SKATER.....only because he is in that business...thats all!
I have been the victim of a bad batch of gas at Havasu, and as a result blew #6 piston to bits in an 2003 300x, and we were just cruising at 60mph. For the little bit of hassel, the AV gas is the way to go....thats what I was told atlesat from MERC. I was paying 2.75 a gallon last season for AV, dont know the current price.

[HavasuDreamin']

This (http://www.toddusa.com/productdetails.aspx?cid=80) product has been great for me. Cheap, and pretty good quality. I fill up the boat before I go on a long trip, and fill up the caddy. Throw the caddy in the back of the truck and off I go. Works great.
:shift:

[Kilrtoy]

Now I have been told as long as you fill up at chevron Mobile or texico , you should be ok......Does this still hold true....

[Propster]

I have just been running 92 in my 2000 Merc 300PM and even that seems almost overkill with that low of compression. It only has 120-122 lbs compression stock. That is not that much compression. Not sure what the 300x has for compression, but it seems like would be about the same. (check to make sure) The only way you could have a problem is if they put unleaded regular in the premium pump. I even ran the mid-grade 89 in it a couple times, seemed fine. You guys are making me nervous though, don't think I will try that again.
I ran my Merc 2.5 with cut heads at 145 lbs compression and had no problems with 92 octane. Ran it hard too. I just ran good Chevron or Texaco gas in it. No Arco or off brands.
If you want to be totally safe, run the avgas. I tried it in my 2.5 when I was in Havasu. Didn't seem to make any difference. The 100LL is rated differently than automotive fuel. It is basically just a super premium. There isn't anything weird in it either, like I keep hearing on some of the boards. It would rate about 96 octane if it was rated like automotive fuel. Mixes excellent with outboard pre mix too.

[HavasuDreamin']

Now I have been told as long as you fill up at chevron Mobile or texico , you should be ok......Does this still hold true....
Ask Tobtek.. :devil:

[HavasuDreamin']

If you want to be totally safe, run the avgas. I tried it in my 2.5 when I was in Havasu. Didn't seem to make any difference. The 100LL is rated differently than automotive fuel. It is basically just a super premium. There isn't anything weird in it either, like I keep hearing on some of the boards. It would rate about 96 octane if it was rated like automotive fuel. Mixes excellent with outboard pre mix too.
This is not correct. 100LL has lead in it, hence the LL = Low Lead. Pump gas does not. You won't see or feel any performance difference between the two. All the higher octane does is keep the motor from detonating and burning up a piston.
Like I said, if you want to run 91 octane in your motors, go for it. You may be fine with it. It may not ever catch up to you...............but if it does, and you get a bad batch like Tobtek, you are going to be out at least $5K on one of those X motors for a rebuild because it usually takes out more than one piston. :hammer2:

[Havasu Cig]

Now I have been told as long as you fill up at chevron Mobile or texico , you should be ok......Does this still hold true....
I would only reccomend Chevron or 76 if you are using regular gas instead of AV. I might be a little biased as a 76 owner, but us and Chevron are the only top tier rated fuels. ;)

[TheLurker]

[QUOTE=TOBTEK]I ONLY WAS POKING FUN AT HAVASU SIG/SKATER.....only because he is in that business...thats all!
QUOTE]
Oh, I didn’t realize you were giving your buddy a hard time.
Having never owned an O/B before I have found this thread interesting.
I have not been on line over the last 3 weeks so I have lost touch with it.
Sorry to hear about your misfortune with the bad batch of gas Tobtek.
By the way Havasu Cig. that is one SWEET looking new ride you have pictures of in the cats and tunnels section. Gotta love those Skaters

[Havasu Cig]

Thanks...
Did you buy the boat in your sig line? If so I have always loved that boat.

[Kilrtoy]

I would only reccomend Chevron or 76 if you are using regular gas instead of AV. I might be a little biased as a 76 owner, but us and Chevron are the only top tier rated fuels. ;)
Chevron is a pain in the ass to get in and out of with a big boat.. So where is 76 in Havasu.....

[TheLurker]

Yes I did.
When it was for sale last spring I wanted to go look at it but we were buying our river house so a boat was out of the question then. Then it popped up again in October and I thought it must have been waiting on me:).
It is not like it is a brand new boat but I got what I thought was a fair price from Boatmaster (Drew) here on the boards. I also don’t know how long I’ll have it. That’s why I did not want to take the deprecation hit on a new one. My wife wanted a more family friendly boat. I told her I needed to fill an urge of mine then if she did not like it we would go for the family boat

[Havasu Cig]

Chevron is a pain in the ass to get in and out of with a big boat.. So where is 76 in Havasu.....
It's across from the ramada on the 95. They sell AV at the pump as well.

[Havasu Cig]

Yes I did.
When it was for sale last spring I wanted to go look at it but we were buying our river house so a boat was out of the question then. Then it popped up again in October and I thought it must have been waiting on me:).
It is not like it is a brand new boat but I got what I thought was a fair price from Boatmaster (Drew) here on the boards. I also don’t know how long I’ll have it. That’s why I did not want to take the deprecation hit on a new one. My wife wanted a more family friendly boat. I told her I needed to fill an urge of mine then if she did not like it we would go for the family boat
Very nice, Can't wait to see it on the water. We just bought a pontoon to go along with the Skater so we did not have to compromise on a "family boat". :wink: :cool:

[TheLurker]

We just bought a pontoon to go along with the Skater so we did not have to compromise on a "family boat". :wink: :cool:
Now you have me thinking. :rollside:

[Havasu Cig]

Now you have me thinking. :rollside:
That was my goal. :D

[BoatFloating]

Talking to the guys at Merc racing they aren't wild about running straight AV gas because it's so dry being LL. 50/50 91 to AV is ok too.They said 91 is fine and a computer on the 300x reads detonation and will make adjustments to the timing. Keep in mind Mercury is aware of bad gas issues and they make their motors to handle that problem. I'm sure they don't want a bunch of warranty motors out there with a chance of getting bad gas. I'm not 100% sure if Toby's piston was caused by bad gas it could of been caused by low water pressure high temps at one time. Toby, did someone tell you for sure it was the gas????

[timewarp]

Talking to the guys at Merc racing they aren't wild about running straight AV gas because it's so dry being LL. 50/50 91 to AV is ok too.They said 91 is fine and a computer on the 300x reads detonation and will make adjustments to the timing.
2001-2004 300X's have no Knock sensor, can't speak for a 2005 but there is nothing in the earlier motors to detect detonation, a quote from the factory service manual "The ECM performs the following functions: Calculates the precise fuel and ignition timing requirements based on engine speed, throttle position, manifold pressure, and coolant temperature" the timing is based on these variables but assumes that the operator is following Mercury's recomendations for fuel type, there is nothing that will cause the timing to retard by using lower octane fuel until the coolant temperature goes up, by then it will be too late, combustion temperatures can increase from detonation quicker than the coolant temperature will respond.
Make sure that you run the best fuel you can afford, I run 100LL or 93 octane pump gas, usually a mixture of the two.
Caleb

[BoatFloating]

2001-2004 300X's have no Knock sensor, can't speak for a 2005 but there is nothing in the earlier motors to detect detonation, a quote from the factory service manual "The ECM performs the following functions: Calculates the precise fuel and ignition timing requirements based on engine speed, throttle position, manifold pressure, and coolant temperature" the timing is based on these variables but assumes that the operator is following Mercury's recomendations for fuel type, there is nothing that will cause the timing to retard by using lower octane fuel until the coolant temperature goes up, by then it will be too late, combustion temperatures can increase from detonation quicker than the coolant temperature will respond.
Make sure that you run the best fuel you can afford, I run 100LL or 93 octane pump gas, usually a mixture of the two.
Caleb
I thought since they had PCM 555 computer and that did have a knock sensor. I guess the not on 300x's. Thanks for the good info. I always run half and half but I'm still a believer that Merc sets their motors up knowing the gas can be a variable. You have to remember on the west coast we don't have 92 or 93 octane because of different factors and Altitude being one of them. We have 91 every where and Merc knows that.

[timewarp]

The PCM 555 computer has the capability to have input from a knock sensor but they don't use it on the 2strokes.
I know that Mercury changed their requirements for fuel on the 300X's over the years, the 2001's stated 92 Octane but the 2004's say 91, not sure when that changed, probably not being able to get 92 in the west, not good to sell a motor that no one can get fuel for. Compression hasn't changed but the ECU's have, don't know if the timing built in the ECU's is different.
I don't know why they would have a problem with 100LL in a 2 stroke, you are adding oil to it any how, I run it straight if it's available. Up here in Washington it's a pain to get Avgas, have to go to the airport. Havasu has it good for fuel.
Caleb

[BoatFloating]

The PCM 555 computer has the capability to have input from a knock sensor but they don't use it on the 2strokes.
I know that Mercury changed their requirements for fuel on the 300X's over the years, the 2001's stated 92 Octane but the 2004's say 91, not sure when that changed, probably not being able to get 92 in the west, not good to sell a motor that no one can get fuel for. Compression hasn't changed but the ECU's have, don't know if the timing built in the ECU's is different.
I don't know why they would have a problem with 100LL in a 2 stroke, you are adding oil to it any how, I run it straight if it's available. Up here in Washington it's a pain to get Avgas, have to go to the airport. Havasu has it good for fuel.
Caleb
Good info Caleb. I know in 2004 they changed the long block on them and I think in 2003 they upgraded the coils that fire on each cylinder. It's called the PCM 03 digital inductive. I thought the same thing about the AV Gas and oil and being dry????

[stoker2001]

This is not correct. 100LL has lead in it, hence the LL = Low Lead. Pump gas does not. You won't see or feel any performance difference between the two. All the higher octane does is keep the motor from detonating and burning up a piston.
Like I said, if you want to run 91 octane in your motors, go for it. You may be fine with it. It may not ever catch up to you...............but if it does, and you get a bad batch like Tobtek, you are going to be out at least $5K on one of those X motors for a rebuild because it usually takes out more than one piston. :hammer2:couldnt of said it any better,even if you mix 30% av you will gain at least three octane numbers which is huge insurance with these stock outboards that seem to eat pistons way to often with calys 91 premium

[Boatmaster]

couldnt of said it any better,even if you mix 30% av you will gain at least three octane numbers which is huge insurance with these stock outboards that seem to eat pistons way to often with calys 91 premium
Both are right on, but one thing that has not been touched on is the fact that AZ gas in most cases seems to be much better than CA. I sell and fix these motors for a living and agree av gas is cheap insurance, and you get less smoke with AV also.

[CrazyHippy]

Both are right on, but one thing that has not been touched on is the fact that AZ gas in most cases seems to be much better than CA. I sell and fix these motors for a living and agree av gas is cheap insurance, and you get less smoke with AV also.
What about the thoughts that Av Gas is "dry?" I'm Pre mixing @ 32:1, do i need to give it a second thought? How about the oil injection guys? Do like the Iron Skillet Car motor guys and add some Marvel mystery oil??
BJH

[Boatmaster]

I have heard that rumor to but have never had any problems running staight AV premix or oiler. I know alot of people mix 50/50 and too each his own.

[Boat Racer]

What about the thoughts that Av Gas is "dry?" I'm Pre mixing @ 32:1, do i need to give it a second thought? How about the oil injection guys? Do like the Iron Skillet Car motor guys and add some Marvel mystery oil??
BJH
I've been running straight AV100 for 15 years... Just like you are doing, 32:1, turn mine 8500 every weekend and have NEVER had one problem... One motor is a 2.4 BP with dual pluged 26cc heads on a fishin' boat & the other is a 2.5 with single plug 29 cc heads!!!
I've heard all kinds of stories & that one too, my favorite is " AV100 only has that octane rating above 5000 feet", that must be some smart fuel, so instead of paying for the octane , we might be paying for it's schooling!!! :hammerhea

[shadow]

Chevron is a pain in the ass to get in and out of with a big boat.. So where is 76 in Havasu.....
Kilr,If you want to use Cheveron,go to the one in the corner of Walmart parking lot.I've been going there for years now and fill the boat and excursion regularly and never had a problem,usually fill the Harley there too.Easy access to the pumps,enterance & exit.Parking lot is alittle tight @ 76 on the southside.We've had alot of cars come through our dealership with failed fuel pumps and other fuel related concerns from other gas stations in town.STAY AWAY from SUPER FUELS!!!! :crossx:

[Kilrtoy]

Thanks Shadow...
You guys are scaring me....with this fuel stuff