rsess

My marina is threatening to stop selling 91 octane this year. I know that the 275 Verado and some of the Mercury Racing I/O's (new HP 850 at least) can be operated on 87. A knock sensor retards the timing or something and the power is reduced. Is this the case with the 300x.

dkwestern

I would assume not, and I wouldn't risk it. Buy some 6 gallon cans and bring gas to the boat. A lot better than melting pistons. I picked up four 6 gallon cans last night at Meijer, they are on sale for $4.84 a piece. By far the cheapest I have ever seen. And it is usually hard to find the 6 gallon cans as well.

rsess

I have 2-300x's and 100 gallon capacity. That's a lot of 6 gallon cans. But I may have to do it. Thanks. Anybody else with information regarding the knock sensor.

Havasu Cig

I would not try it. I am going to run A mix of 91 and AV-Gas (100 octane) in my 300x's just like I did on my 2.5's. Mercury actually reccomended running AV if available, which it is in Havasu. I would think 87 would not run well at all, especially if it is warm where you boat.

Firewalker

You cannot run 87 in a 300x it WILL blow up
There is a fuel addiive on the market called TK-7 made by Tal indudtries, it works...... and is the ONLY additive I know of that does. It is like Crack for motors.
Lastly, Merc does not will not and has not ever recommended AV fuel for it's new ( last 20 years ) hi per motors. Av fuel is for air cooled 1000 foot per min motors, not 3-4000 foot liquied cooled 2-cycles. AV has an additive in the fuel that dissolves oil, this is to prevent plug fowling in an air plane motor. In a 2-cycle it spells death. NO matter how much oil you add it will win, even with double oil your motor will wear out both the rings and bores 50% faster. If you have ever heard that AV runs dry......... that is the reason.

RT

Havasu Cig

Well I can tell you that Merc HAS reccomended running AV in both the O/B boats I have had. The current has 04 300x's and the other had 2000 280hp 2.5's. Lot's of guys at Havasu are running Av because you can buy it at the pump at several stations and the 100 octane is good insurance for 120 degree temps. Nobody that I know has had any problems.

Firewalker

Well I can TELL you your motors wear out faster, who ever told you to run it needs to take a chemistry lesson or two. Yes it will stop detonation, but you WILL wear it out.

RT

timewarp

Do you have website or phone number, where do you get this, I have been looking at Max Lead and Octane Supreme 130, but have only heard of people using them in Four strokes(big block Mopars) they are supposed to work good.

Thanks for any info you can give me.
Caleb

Firewalker

http://www.pitstopmarine.com//index....799d43e0b33103

Try that.

RT

rsess

OK I did the math. That stuff requires 1 ounce to the gallon of 87. That means 1 gallon does 130 gallons of gas. At $115 plus tax plus shipping for a gallon of the stuff, it works about a buck a gallon above the price of 87. Those $5 red cans are looking good. Any body know a good way to transfer gas from them instead of holding them by hand. Thanks for info.