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Higher Octane Fuel = Timing Issues?
#12661794
03/07/18 11:29 AM
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Joined: Feb 2018
Posts: 57
ConwayFishy
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Outdoorsman
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OP
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Could higher octane fuel in a Yamaha Pro 50, 2 cycle engine cause timing issues? When my lower idle kicks in 30 seconds after starting up, my engine will eventually cough and then die. This only happens when its idling. I can run it wide open and its like the day it was made. Thoughts? Opinions? Suggestions?
Motor has minimal hours on it. It was used 8 times per year from 1991 - 2014. The rest of the time it was under a cover inside of a barn. Always winterized and old gas was burned out of it before winter.
Dad, Husband and the Proudest Member of the Fightin' Aggie Class of 2008
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12661837
03/07/18 12:25 PM
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Joined: Jan 2005
Posts: 17,004
Pat Goff
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Not unless it's gone bad, which doesn't take long nowadays.
Pat Goff Seadrift TX
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12661962
03/07/18 02:08 PM
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Joined: Jan 2009
Posts: 1,649
spankyttx
Extreme Angler
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Extreme Angler
Joined: Jan 2009
Posts: 1,649 |
bad fuel or it's compression testing time
LI-SI-WI-NWI
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12662311
03/07/18 05:22 PM
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Joined: Jan 2009
Posts: 1,649
spankyttx
Extreme Angler
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could be the idle circuits in the carb are getting clogged, those passages on the yami carbs are tight or it could just need adjusting
you didn't say what rpm's it was idling at before or if it is fresh gas but i would start with a compression test and check the carb idle adjustment, it could have backed off a bit, if that shows to be good, i would run a can or two of seafoam in a couple gallons of gas threw an external gas can at idle to see if it cleans up, if it doesn't clean up and it has good compression, i would lean towards the carb needs cleaning, that's all i got
LI-SI-WI-NWI
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12662750
03/07/18 09:19 PM
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Joined: Jul 2012
Posts: 2,183
boocat
Extreme Angler
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Extreme Angler
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yeah, I'm thinking the non ethanol gas I can get here that I want to start using is 92. Shouldn't be a problem?
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12662836
03/07/18 10:12 PM
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Joined: Jun 2016
Posts: 6,854
V-Bottom
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87 Octane is what you need. I heard higher octane E-Free gas will make the engine run hotter.
Texas Anglers Recognition Program TPWD Official Weigh Station,77563 Coastal Bend Weigh Team, Cert. Weigh Master USMC66'- www.troutsupport.com
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Re: Higher Octane Fuel = Timing Issues?
[Re: V-Bottom]
#12663139
03/08/18 01:45 AM
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Joined: Apr 2017
Posts: 12,181
tmd11111
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87 Octane is what you need. I heard higher octane E-Free gas will make the engine run hotter. Actually its the opposite and too high of an octane will lead to excess carbon buildup
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663213
03/08/18 02:36 AM
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Joined: Jan 2009
Posts: 1,649
spankyttx
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higher octane burns hotter with less carbon build up
LI-SI-WI-NWI
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Re: Higher Octane Fuel = Timing Issues?
[Re: spankyttx]
#12663240
03/08/18 02:59 AM
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Joined: Mar 2015
Posts: 499
Cat finder
Angler
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Angler
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higher octane burns hotter with less carbon build up High octane burns cooler, which is why most run it to remedy detonation issues. No need for plus grade fuel mid grade is just fine.
If the fish don't bite your not baiting right...
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663260
03/08/18 03:14 AM
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Joined: Jan 2009
Posts: 1,649
spankyttx
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lol, better check your facts, it burns hotter and longer than low octane, less carbon build up, high octane is used in engines with higher compression to eliminate pre detonation knock before tdc (top dead center). so low octane will burn out before tdc causing the knock, high octane burns over the top past tdc, eliminating pre detonation knock
LI-SI-WI-NWI
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663295
03/08/18 03:44 AM
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Joined: Mar 2015
Posts: 499
Cat finder
Angler
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Angler
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Posts: 499 |
Its just more resistant to self igniting at a given pressure or temperature. It even has a higher auto ignition temp. That being said it can't burn more hot as it would indeed have a shorter burn rate.
Last edited by Cat finder; 03/08/18 04:03 AM.
If the fish don't bite your not baiting right...
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663308
03/08/18 04:09 AM
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Joined: Jan 2009
Posts: 1,649
spankyttx
Extreme Angler
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Extreme Angler
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higher octane burns slower, low octane burns faster, think of it like this, a low octane fire is like a flash fire, poof and its gone, a high octane fire will be like a bonfire, blazing and hard to put out. which one would be hotter?
LI-SI-WI-NWI
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663391
03/08/18 09:36 AM
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Joined: Apr 2015
Posts: 1,818
Curtbass
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Spankyttx. You're partly right. Octane is a flame retardant. It burns slower the higher the octane. It doesnt increase the temperature of the flame. Just burns longer. The amount of heptane is what increases flame temperature. Higher octane 89,91,93 will continue to burn past TDC on the timing issue. So , technically it burns too long for an engine designed to run on 87 octane fuel. Its got the same amount of heptane in most grades of pump gas. So temperature is same , only the burn rate changes by upping octane. In other words , your paying more for the higher octane & not beneffiting from it IF your motor is designed to run on 87 octane. It most likely can cause MORE carbon buildup because its not burning ALL the fuel at the proper time & an incomplete burn will result in more carbon residue being left in cylinder & in ring glands & behind rings on each stroke. Costs more for less efficiency. Higher compression motors call for higher octane to PREVENT detonation BEFORE needed. Hogher octane slows burn rate down until piston is just before TDC to take advantage of getting more fuel into it before before starting compression stroke & Not igniting prematurely from compression. . Thats the basis of why a higher compression motor produces more power. It burns more fuel on its power stroke. Thats why timing is different on a higher compression motor.
Last edited by Curtbass; 03/08/18 09:40 AM.
ELITE POWER SYSTEMS/ Elite Fishing Products Lithium Battery & Charging Systems, Soft Plastics, Tackle,Tokyo Rigs Tight lines & stay safe out there.Gods blessings
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663433
03/08/18 12:26 PM
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Joined: Feb 2018
Posts: 57
ConwayFishy
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I found the issue. There was this small plastic box that controls the timing near the throttle control in the engine. Yamaha wanted almost 700 to replace this box the size of a two cigarette boxes. It's black and has 4 little marks on it that mark low idle, high idle, mid throttle and wide open. I simply, slightly, adjusted where the engine idles by raising it just a bit from the lower setting...maybe 1/10 of an inch. The thing really idles smooth in high idle and low idle now....and doesn't die... I also adjusted the carburetors as needed. SO it wasn't the gas, but was a timing issue indeed.
Also, I replaced the bolt that actually stops the throttle control when its wide open. I guess its kind of a control bolt that keeps the thing from going past that last little tic mark on the black box. Since I raised the lower setting to stop the coughing, I put a bolt in there with a slightly larger neck and in wide open the throttle stops at that last mark where it's meant to instead of going 1/10 of an inch past.
Thanks for the replies. I'll run 87 octane fuel in it from now on and avoid mid grade. See how that works. Also threw a can of sea foam in the tank to help get any gunk out.
Dad, Husband and the Proudest Member of the Fightin' Aggie Class of 2008
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Re: Higher Octane Fuel = Timing Issues?
[Re: ConwayFishy]
#12663444
03/08/18 12:36 PM
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Joined: May 2003
Posts: 11,586
gary purdy
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Definitely will have more carbon build using higher octane. Seen personally on all kinds of motors. Midgrade fuel is what most outboard manufactures recommend. Timing and operating temperature effects the fuel burn also.
The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD
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