Gas additives --Help??? Other fuel questions

[retired chem teacher]

I still try to buy ethanol free gas for all my small engines and add sta-bil and a little mystery marvel oil to each 5 gallons that I buy--- has worked for me for years so guess I will stay with it  --have a riding lawnmower with over 1000 hrs and still running with little or no oil consumption between 50 hr oil changes ---only add sta-bil to boat gas and occasionally sea foam--- I have heard and seen problems with hoses and gaskets using ethanol fuels so try to avoid- I am old and so are my boats and motors but both me and boats are still going for now --still curious about running engine with fuel line detached until it dies for the winter--I always did this with a 2 stroke 25 hp merc carb engine--50 to one mix not oil injection--and not efi--now don't have that motor anymore but still running --now I have 1998 merc 150 efi 2 stroke that the oil injection went out so I mix oil in gas in boat tank--will running it dry so to speak mess up the efi or something else.???

[tjm]

https://www.amazon.com/REV-X-Super-Tester-Flex-Ethanol/dp/B073HLSVHX

test your fuel for ethanol with that ^^^^ although I've done the same thing for 40 years using a jelly jar  with painters tape on it.

[fishinwrench]

9 hours ago, Ketchup said:

Possibly, but the recommended octane ratings differ, as should be. Same with automotive engines, RC engines, etc. so a 250 should technically run poorer with 87 vs 89 vs 91 vs 93.  
 

Picture one of those go fast, 200 mph LoZ boats running on 87, or an NHRA funny car running on 89.  

Honestly this isn't even worth talking about🙄 

Air temp, manifold pressure, engine temp, and exhaust O2 are all used by the ECM to to alter injector pulse width, ignition timing, and manifold vacuum.   So unless you feed it something far to one end or another of the combustible spectrum (water or diesel fuel) then the torque output SHOULD be relatively stable.  

Therefore, without precise monitoring equipment you aren't going to notice a  difference between 87 or 91 octane fuel anywhere but in the thickness of your wallet.  

As far as "HIGH PERFORMANCE" altered motors are concerned.... Outboards are already"high performance" by design, so tweeking/flashing for even MORE performance comes at a cost.  And that cost is

R-E-L-I-A-B-I-L-I-T-Y.   Engines tuned to go extra-fast don't do it for very long.   You'll only get there quicker if the distance is short.  

[Ketchup]

36 minutes ago, fishinwrench said:

Honestly this isn't even worth talking about🙄 

Air temp, manifold pressure, engine temp, and exhaust O2 are all used by the ECM to to alter injector pulse width, ignition timing, and manifold vacuum.   So unless you feed it something far to one end or another of the combustible spectrum (water or diesel fuel) then the torque output SHOULD be relatively stable.  

Therefore, without precise monitoring equipment you aren't going to notice a  difference between 87 or 91 octane fuel anywhere but in the thickness of your wallet.  

As far as "HIGH PERFORMANCE" altered motors are concerned.... Outboards are already"high performance" by design, so tweeking/flashing for even MORE performance comes at a cost.  And that cost is

R-E-L-I-A-B-I-L-I-T-Y.   Engines tuned to go extra-fast don't do it for very long.   You'll only get there quicker if the distance is short.  

I need this thing fixed then.  Before the flash from HydroTec i ran 89, as that is the recommended  octane. The guys told me when i picked my boat up that it will run on 87/89 but will run better on 91. I had just filled up when i had the lower replaced and the flash done, so i ran that 89 for several trips.  My speeds were 78 light loaded, but the hole shot and mid stunk.  After i ran that tank i filled up with 91 and added some booster to it as well. After putting around Pomme i decided to see what it would do, so from the Nemo bridge to the dam i let it go.  The hole shot was more noticeable, mid range was great, and speed was 81.2 mph.  Light chop on the water last January.  
 

Since then i have ran some 87 in it and it was not the same boat. It has its best days with 91 ran through it. FXP 27 prop

[aarchdale@coresleep.com]

21 minutes ago, Ketchup said:

I need this thing fixed then.  Before the flash from HydroTec i ran 89, as that is the recommended  octane. The guys told me when i picked my boat up that it will run on 87/89 but will run better on 91. I had just filled up when i had the lower replaced and the flash done, so i ran that 89 for several trips.  My speeds were 78 light loaded, but the hole shot and mid stunk.  After i ran that tank i filled up with 91 and added some booster to it as well. After putting around Pomme i decided to see what it would do, so from the Nemo bridge to the dam i let it go.  The hole shot was more noticeable, mid range was great, and speed was 81.2 mph.  Light chop on the water last January.  
 

Since then i have ran some 87 in it and it was not the same boat. It has its best days with 91 ran through it. FXP 27 prop

Im with Jerry on this one, i had my ECU flashed on my old boat and if i didnt run 91 which the tuner told me to run it ran like crap.  I have friends with cars that have been tuned to run to a certain fuel. 900hp on 93, and 1100hp on ethanol. 

[tjm]

2 hours ago, fishinwrench said:

Air temp, manifold pressure, engine temp, and exhaust O2 are all used by the ECM to to alter injector pulse width, ignition timing, and manifold vacuum.   So unless you feed it something far to one end or another of the combustible spectrum (water or diesel fuel) then the torque output SHOULD be relatively stable.  

when they flash the ECU don't they change the parameters that set those things? More narrowly define the operating conditions? If the software changes in pulse width and timing favor higher octane, wouldn't that retuning cause poorer performance with lower octanes?  I'm not up to date on this sort thing, but it seems kinda  like recurving a distributor advance. 

[fishinwrench]

What y'all are talking about is NOT ECU TUNING.....it is partial ECU deletion.   Your control system is ignoring O2 data, MAP data & engine temp data.   Perimeters of injector pulse and ignition timing are back to a preset analog.

It is basically not being an ECU anymore.   Might as well scrap the vapor separator and air plenum and just install carbs, because you gave up fuel efficiency and emission control......which is what you initially paid for when you bought that Hi-Tech water stirrer.  

And mark my word.....that sumbitch is gonna blow quicker than it would have if you'd left it alone.   Promise ya that. And the warranty on your replacement powerhead......might as well not even consider it. 

I bet they didn't recommend a different spark plug for your new "ECM FLASH" did they ?         If it was legit then they SHOULD HAVE.

[Ketchup]

I don’t run anything i own very hard, but i do know it appears to run on less fuel now than it did. I assume due to it not needing to try so hard to get out of the hole, or have better mid range performance, but my fuel consumption as a whole has gone down since i had it flashed.  
 

When they did the work, i had them do a full tune up on the motor, so I assume again that plugs would have been part of that. What ones i have no clue. I used to enjoy tinkering with engines, but the last 10 years it’s easier to drop it off somewhere. I do do my oil changes on my trucks so i can keep my man card. 

[Flysmallie]

On 9/17/2023 at 9:41 AM, Ketchup said:

NHRA funny car running on 89.  

They do just fine on it during a burnout. But of course they burn nitromethane for a run down the track. 

[aarchdale@coresleep.com]

20 hours ago, fishinwrench said:

What y'all are talking about is NOT ECU TUNING.....it is partial ECU deletion.   Your control system is ignoring O2 data, MAP data & engine temp data.   Perimeters of injector pulse and ignition timing are back to a preset analog.

It is basically not being an ECU anymore.   Might as well scrap the vapor separator and air plenum and just install carbs, because you gave up fuel efficiency and emission control......which is what you initially paid for when you bought that Hi-Tech water stirrer.  

And mark my word.....that sumbitch is gonna blow quicker than it would have if you'd left it alone.   Promise ya that. And the warranty on your replacement powerhead......might as well not even consider it. 

I bet they didn't recommend a different spark plug for your new "ECM FLASH" did they ?         If it was legit then they SHOULD HAVE.

My Opti had 813 hrs when i flashed it and a little over 1100 when i sold it. Barely used any gas at all. Only problem i ever had was a coil go bad. Did the same thing with my fourwheeler, I have a polaris 450 but it is just a detuned 570. Sent the ECU in and they tuned t to run on 91 and not it has 2hp more than the 570's