Fuel with menthanel
 

I run a pair of 300 ProMax oil injected and fuel injected outboards on my ChrisCat. I was low on gas and had to put in some of the midgrade additive added fuel here in Michigan. Will it hurt the engines, and what should I do, I have since put in 93 octane fuel.

Thanks Ron Luks:eek:

add some toulene and bring the octane up:ernaehrung004:

Technically, you should not have to run the high octane in those particular motors. If they are just standard Pro Max 300's. Only the Bridgeport engines over 260 Hp require better fuel. You will see better fuel economy though with 92+ octain. But not enough to justify the higher price. Something else you should consider doing is removing the oil injection. Pre-mixing your fuel is always a better deal, though not as convinient. Mercury makes a plastic plug for the old pump hole in block. Make sure to get the "long" one to hold in brass bushing. Powerhead removal is not nessesary. 16 oz's of oil to 6 gallons of fuel. Hope this helps !!!!!!!!!!

RainsPerformanceMarine
Afton, OK
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fuel
 

Thanks for all the info, I do have the 300 HP ProMax's, I only burned approx. 40 gals of the lower grade (mixed with approx 40 gals of 93) leaving approx 40 gals in the tanks, and have added 100 gals of the 93 octane. With what I have read I guess I should be alright. I forgot all about tolulene, I used to run it years ago in my drag cars, old tricks never go away, with the price of gas now it makes sense to buy tolulene.
Thanks Ron

Technically the gas you bought has ethanol,not methanol,the main thing besides octane is it leans out your motor but most gas now has ethanol in it. I looked for tolulene myself a few weeks ago and most places no longer have it. Tolune is 110 octane,race gas does the same thing for less if you wanted to boost your octane,Smitty

Artic go to your local Sherwin Williams paint store they'll have it we pick up 55 gallon drums from ours .in a pinch Menards sells it also :ernaehrung004::ernaehrung004: you can pump 87 to 100 octane for pennies on the dollar . 700 gallons 87 octane and add 110 gallons toulene :drink:

The oil injection on the 300 pro max has proven pretty reliable why would he remove it?
Not just the "bridgeport" motors that have over 260 horsepower require higher octane fuel.

I've been using TORCO Accelerator $$$ but tought:p about going the toulene route.
How much does a 55 gallon drum sell for?

UPROKTOY.................some people never learn do they......A stock promax does not require higher octain fuel. You need to do your research on compression in the 300 PM. Do you know what that is????? I have probably forgotten more about outboards than you will ever know............

Here in good old CA, we are limited to 1 gal at a time.



Darrell.

When I first saw this thread I thought someone had figured a way to get horsepower from menthol cigarettes.

**** you must be really really smart...my favorite comment....boy do I feel stupid.

Thanks for your insight. I can tell your an expert. I digress.

funny, I coulda swore that mercury recommended 92 octane on the 300 pro max and the 300x promax

well I should state that I know for FACT that the on the 300x 92 octane or better is called for...I'd have to look the 300 pro max up...but your the expert.

I might be wrong on this, but I think 300 pro max compression is around 120-130 not to be more then +/- 15 lbs . Page 1-21 of the service manual. Can you show me otherwise?

you're an idiot.

3.0Ls don't need oil injection blockoff kits, because even the old ones dont have POS plastic drive gears.

bridgeports are 240ish HP. 260s 280s and 300 drags are not bridge port engines. they arent even the same displacement :rolleyes:

a 300 promax requires 91 octane minimum.

and you cant spell worth a ****. :grinser010:

He forgot more then you ever knew about outboards. Don't argue with him.

Go take the potatoes out of your bilge and get your bridgeport 280 running on some 77 octane and go for a boat ride since your not currently under seige by a hurricane.

To the original poster, I personally wouldn't chance any guess you didn't feel comfortable with. I always run any gas that I think may be questionable through my truck and re-fill my boat with new fresh fuel.

i'm sorrry, i didn't know this was a spelling contest. my bad. 120-130 #'s of compression is standard for any 150-300 hp, stock production Mercury . If they don't require the higher octain, they why would this gentleman need to run it in his. All I was trying to get across was the fact that he can't hurt his motors by running the lower grade fuel........

Interesting way of getting your point across...So if mercury recommends high octane fuel what in your vast experience of forgetting more about outboards then the rest of us leads you to believe it's not necessary?

I'll check our local sherwin williams paint store. When I was looking a few weeks ago I checked the building supply center,lumber yard and small town hardware store in the hick town I live close to but all three said they no longer sold it,they used to have it in 1 and 5 gal cans but didn't know why it was no longer available/stocked. Until 2 weeks ago I could buy torco 110 for 4.89 a gal,now it finally jumed up to over 6$ a gal. I throw 10 gallons in with 50-60 gals 93 octane when my boat hasn't been run for a few weeks and I know I'm going to be holding it in boost to help ensure my octane hasn't degraded from the poor characteristics of ethanol gas sitting. This spring was the first year my local station no longer sold 93 octane without ethanol,Smitty

do the math........and im out................

so I guess that mercury recommends 91 octane or higher in their owners manual just because they feel like it then? :rolleyes:

What math is to be done? You do realize that compression alone is not the only factor to determine which octane fuel a 2 stroke outboard engine requires right?

Typical I don't have anything to back up my opinion so I will just call you stupid internet answer....

Congratulations.

same thing here i checked home depo as well as sherwin williams they both no longer carry toluene here.:(

Smitty around here home depot,menards carry it just way more expensive by the gallon .sherwin williams brings it in for us and last 6 drums were 200.00 a barrel ... you may want to google toulene in your state/town and its still around :ernaehrung004:

To answer the question at hand, you will be fine.
Merc does indeed rec 91/2 oct. It is not necessary, you can get by with 87 ( if it is fresh and ethanol free ). Not that I would, but you are not going to hurt your motors, at least not with detonation.
If you want a booster that actually works, get TK-7. It is the ONLY octane booster that actually helps.
As and owner of a 225 carb bridgeport, a 240hp EFI bridgeport, a 245 carb 2.5, a 260hp 2.5, a 280hp 2.5 many 300PLUS hp 2.5 drags, a few 300 pro max's and a 300x... and a licence to work on them, I can assure you I know more about them than the stump who clearly forgot more than the rest of us!.

If you want a booster that actually works, get TK-7. It is the ONLY octane booster that actually helps :rolleyes: really :cool:

Ya gotta love it with all the wisdom on these forums....:crazy:

Any hydrocarbon with a higher effective octane rating can be mixed homogeneously into a "base fuel" hydrocarbon with a lower effective octane rating with the net effect of raising the octane of the base fuel. It isn't limited to a particular brand name or chemical makeup.

93 octane fuel is regularly mixed with 87 octane fuel IN THE PUMP ITSELF to deliver midgrade 91 octane into your car.

Toluene is, and has always been, an effective "octane boosting additive" to pump gas.

There are, however, OTHER MAGIC CHEMICALS (remember tetraethyl lead???) that, when added in small amounts to unleaded base stock, can improve "octane" dramatically by inserting themselves in the long chain molecules and providing a "buffer" action in the flamefront behavior.

No need to argue whose octane booster is bogus, and whose is glorious. Many of the AutoParts brands of octane improvers, however, are MINIMALLY effective. When they speak of boosting your octane by two POINTS, they are talking about going from like 90 to 90.2 - keep that in mind.

And I hope we ALL are firmly aware that OCTANE is an empirical measurement of how RESISTANT a fuel is to uncontrolled combustion. It isn't a measure of the energy content (heat content) of a given fuel. High octane fuel can be run at a higher pressure and temperature while providing detonation resistance. You want a fuel that burns evenly rather than explodes - that's the goal. As a hard and fast rule of thumb, given a low octane gasoline and a high octane gasoline, the lower octane gasoline will contain MORE energy per ounce than the higher octane fuel. Test after test will show that running the lowest octane fuel that will stave off detonation in your engine will deliver the best fuel economy and power - when all other engine parameters are identical. All of us who have cars that run "better" on premium are experiencing what happens when the computer avances the ignition curves to take advantage of the higher octane fuel we've poured in. If we had non-computer motors, we would have a NEGATIVE performance gain when adding higher octane (although not enough to feel).

In the case of a 300 ProMax, it's a motor that's happy on midgrade fuel.

Ethanol in your fuel? Yeah, it will show that it runs leaner in your motors, but unless you are running a race tuned motor, there is generally enough fuel metering leeway to ignore the difference. Generally, that is.... I have a 68cc 2 stroke Scooter that belongs to my son, but I ride to the shop occasionally. It's tuned to the edge of life, and runs impressively. Add ethanol in the fuel and cool weather, and it will no longer start when cold, and requires a jetting change. You won't have that issue on your 300 ProMax.

A 300X is a smaller, more highly tuned motor. Requires better fuel.

And cranking compression on a 2 stroke motor doesn't mean much by itself. Unlike a 4 stroke motor that has an "intact" cylinder bore, a 2 stroke is perforated with ports. These ports let pressure escape, ESPECIALLY at cranking speeds. Two different 2 stroke motors cn have the same cranking compression with one being a low rpm low performance mtor with low octane requirements, and the other being a racing motor with wild porting that requires higher octane.

Sure, given the SAME motor, raising the compression also raises the cranking pressure, but raising the exhaust port lowers the cranking pressure. I've got a 2.4 Merc that had 135 psi at baseline. I reshaped the compression chambers and brought the compression up to 185, then I raised the exhaust ports .060" and it dropped to 170. You get the idea. Cranking compression doesn't mean much in a two stroke. Combustion pressure at operating rpm is what matters.

Bridgeport Mercs have a larger exhaust port opening that is "too big" for the piston ring to remain stable. For that reason there is a bridge in the center of the port to support the ring. When you REALLY start modding those motors for serious power, the bridge gets too hot and "melts" out of the way because there isn't enough beef behind the bridge. Then you lose the cylinder. We had better luck going wild with standard finger ported oval port blocks when we started going nuts with them. Good luck to anybody running a Bridgeport who starts spraying nitrous, etc. Better hold your mouth just right and live & die by the fuel pressure warning light.

Now why are all of us fussing at each other?
If there are people on here who have "forgotten more about something than somebody else will ever learn" then maybe they need to take a memory course. Why the crap are they forgetting so much, and if they are, why do they want to brag about it.

There were probably people on here who were "building motors when I was crappin yella" but what is that supposed to prove? All I can tell it means is that they learned how to put together an old motor when I was eatin strained peas. Big deal. Seniority is not necessarily a valid qualification for the guy you want keeping your modern motor running right. Neither is forgetfulness.

Back to the thread - it's a shame that our fuel is full of alcohol, not cause it will blow up our motors, but because we don't go quite as far on a gallon, and because the rubber parts in our fuel system harden on exposure to alky.

peace out
mc

Great post MC.
Thanks!

Mc,Very impressive,what a great post,thanks.Enjoyed the read. "Peace,out" been a while since I've seen that one.Memories.....Kinda made me smile. Bob

Great post MC, a lot of info in a few short paragraphs that even I can understand. I know now I didn't hurt the engines and am grateful for all the imput by everybody and know the course I will now follow. Thanks again, all of you.
Ron