fuel

[Capitalist]

Merc wants to sell parts. The resaon the pistons fall apart is becase merc won't spring the extra 5 dollers per motor (that is not a typo)for pistons that a 10 times as good. Merc is the king if engeneered obselecence....Mr. Kiekhafer is rolling in his grave.
I should mention that you will not blow up a motor on AV, just that you will wear it out faster ( a lot faster ). And that the extra expnse is not warranted (fuel and rebuild).
ET

[HavasuDreamin']

I run 155 PSI in my merc. I run Av-gas straight, no mix, and have been doing this for more than 5-years. No problems. Motor still has excellent compression. I have been in very reputable shops before (Dick Sherrer Marine & Lakeland Marine) and seen pistons with holes in them, melted pistons, etc. In each case, the engine builder said........."look what bad gas can do, make sure to run good gas and synthetic lube."
I don't understand your point that av-gas will harm my motor (lower life expectancy). I have more than 100 hours on my 155 PSI Merc running nothing but Av-gas. Top RPM is in the 7200 - 7400 range. I would think that if Av-Gas was going to wear it out sooner, it would have done so by now. By the way, do a search and check out what the blower motor guys say. This topic has been covered multiple times. Most of the Blower motor guys run av-gas as well. Few to none have problems.

[Capitalist]

100hrs is not a lot of time, compression does not tell you the condition of your rings, only a Leakdown test will tell you that. Your motor is a 2 cycle, not a blown 4 cycle. Consider that one requires oil in the fuel to run and the other doesn't........... two very different animals please don't make the comparison.
ET

[ed bullock]

okay i have heard alot of input on this suject i talked to a merc rep he told me not to use premium fuel because it sits and gets old. he says it dosent have the additives that mid grade does. so what about buying mid grade wich is 87 octane where i live and mixing it with a fuel that vp makes called c-12 made at 108 octane leaded made for marine use it is expensive but is it worth going the extra mile and using a synthetic oil.i have learned alot from every one here and want to say thank you fot all the info.

[Capitalist]

Now you are talking.
Though, the C-12 (that is what I run but at 100% with 210psi compression)will loose it's octane very quickly if left out.
A little trick is to put a valve in the fuel tank vent and close it when you store the boat.
Use, Penzoil 100%, Klotz, or the best in the business Alisyn for motor oil.
ET

[ed bullock]

does everyone agree that c-12 is a quality fuel? it is built for 2 strokes the price is high but if it is able to prolong the life of your power head it may be worth the money. av-gas guys have you used this product ? can it be mixed half and half and still have the edge over av-gas ? this seems to be a hot topic that every one can use information on .

[Tom Brown]

Ed, what engine do you have? Static compression is not the only factor in determining the type of fuel an engine requires.
I run premium non-lead in my stock 1989 XR-4 and it does just fine. My static compression is 130 psi.
My $0.02
Tom Brown

[ed bullock]

tim i have 1997 2.5 260

[Capitalist]

Ed if that motor is stock, run 91 oct or better and forget all the above. That motor will even run on 89 oct if you have to but, I would not use it as daily fuel.
And yes C-12 is one of the best fuels for a 2 cycle C-44 is better, and Sunoco Purple (CAM 2) is also very good.
ET

[gregg canavan]

gee guys, I run mid grade, 89 octane for a while now, I havent had any trouble. I'd like to spring for the 93 octane but I hold 200 gals and we'll go through 300 gals in a weekend...the extra money really adds up. Not to mention the oil at 15.00 a gallon
89 octane is ok, isn't it?