Re: 110 octane fuel
I've been following this thread with hopes that someone would explain why "high octane" fuel is advantageous in some engines and "waste of money" in others. There have been rants about cars and bikes running faster with high octane fuel but none of that has been backed up with proof other than "I seen it!". So lets set the record straight.
1) As mentioned about a dozen times, high octane fuel is used in engines THAT CAN USE IT. What that means is if the engine is a high compression design that would detonate with 87 octane, you MUST USE high octane.
2) Air cooled engines like airplane engines, run hot. Hot engines tend to detonate. Guess what -- high octane fuel is REQUIRED.
3) Since the advent of electronic fuel injection, vehicles have had knock sensors. A knock sensor detects detonation and when it does it retards the spark. So if the characteristics of the engine is such that the engine does NOT detonate on 87 octane, the knock sensor advances the timing to get optimum power for the current load of fuel. In that particular engine, adding higher octane fuel MAY allow a performance increase since the knock sensor and ECU may have a bit more advance to play with. Another car with the same type engine may have tolerances that doesn't allow that much advance. As for the "old Chevies" running better on high octane fuel, they had 9:1 or higher compression ratios and with no way to alter the timing when detonation occurred, premium fuel was required. If you manually advanced the timing beyond factory settings for "regular" fuel, certainly premium would help. However, compare those compression ratios to the 6.5 - 7.5:1 compression on outboards. Low compression and hard to light off high octane fuel do not go together.
4) You asked if there was timing advance on outboards. I would first suggest you actually buy a service manual for your engine so can learn about them and rationally discuss it. Yes, as you open the throttle, the timing advances accordingly. Now I'm sure you are going to jump on this and advance the timing so you can get more power. What you will do is screw this engine up worse than you already have it and likely hole a piston. Don't you think the factory had optimized the settings for reliability, performance and economy?
5) You said you can't make the engine idle but you certainly could if you disconnected the throttle cable, did the link&sync as outlined in the manual, and then readjusted and attached the throttle cable. Link&sync is a multi-page process in the service manual. If you do obtain said manual, you are advised to start at the beginning and go to the end following that procedure to the letter. You cannot start in the middle and have a decent running engine (except by dumb luck).
6) You cannot clean a carb by dumping any stuff down the throat. Carb issues are generally "internal".
7) While you may be on a budget, buy one less six pack and spend that money on proper gasket material.
8) Two strokes don't have valves so indexing spark plugs is generally not required or advantageous. It is used on some DFI/EFI engines to get the plug oriented for optimum firing of the fuel charge from the injectors.
9) If you are so certain your engine has an electrical problem why are you pursuing premium fuel as a cure for the problem. Don't you think some actual diagnosis would be helpful?
10) You admit to running old fuel. Even if it runs fine in another engine it may not be fine for this engine.
11) Stop comparing what happens with premium fuel in a car, motorcycle or airplane engine. They are all different, have different requirements and all are vastly different than your two stroke outboard that is 40 years old.
12) If you get better advice from another forum, let us know where that forum is. But remember, just because YOU believe it is a better forum does not make it so. Nor is it valid if you simply get the answer you want to hear. I would think at this point you would have come to the conclusion that you have a very poor understanding of this entire octane requirement issue and outboards in general.
13) The last bit of advice is to keep your issue to ONE thread.
