Vinny P

I started this thread with myself and a good friend in mind. We both took our first runs of the season today and found out that the fuel docks we normally fuel up at, no longer carry 91 octane. We can only get 89. We have heard that there may be 1 place that may have 91. However, its a pain in the a$$ to get there, due to many long no wake zones. So, for now, lets say we are stuck with 89. Jugging fuel to the dock is not possible either.
Some may say, add octane boost. I am not a believer in that stuff. From what I know and have researched, the cost and the amount you have to add to make such a small difference in octane, doesnt make it sound to appealing. In the past, when I was into running high compression engines in street cars, I used to mix in some race fuel, maybe Cam 2 or VP, with pump gas. That was easy, after all, compared to a boat, a car sips fuel.
Now for our engine specifics.
My friends engines are the easier to describe. He simply has 575SCI's. Fresh rebuilt, nothing added, everything was built back to factory specs. Ofcourse, Merc recommend 91 octane. Has anyone run these engines on 89?
Mine is a bit more complicated. I am running new built, NA 565, 10 to 1 compression, aluminum heads, closed cooling. No EFI, no computer to control the timing. Just a simple Carb and an MSD. I normally run 36* advance, locked. With the closed cooling, my water temp runs about 180*. I am thinking I can lower the water temp some, that may help lessen the chances of detonation. I have aluminum heads, that has to help suck out some combustion chamber heat. The fairly large bore, 4.530 may help a bit. I suppose I can add a knock sensor. At least that will tell me if there is something going on. Does anyone run a simliar combination on 89?
The next question I have, does anyone have a successful, proven formula for increasing octane?
If I wanted to simply add some race fuel to the mix, is there a formula for calculating how much is needed to bump up 89 to say 91? Is it as simple as calculating the percentage of 89 and race fuel, to come up with the new octane. For example: 5 gallons of 100 octane added to 5 gallons of 90 octane would make 10 gallons of 95? That would be nice, but it seems that may be too simple a formula.

LV

I have a similar set up as well but new motors this winter , we do have 91, my builder said to splash 10-15 gallons of 110 in there just to make sure you are above 91.

FIXX

iTrader: (2)

Contact your local fuel oil distributor,some one who delivers fuel to construction companies tanks in their yards..see what it would cost for them to drive their mini tanker and fuel up yours and friends etc etc etc..if you can get enough boats together and your close to shore I'm sure thet will fill them up and it should keep the cost down..

Vinny P

That would be a good idea. Unfortunately, we both keep our noats at a local high and dry here on Long Island. The owner doesnt want to see anyone filling up their boats on his property. Insurance regulations I guess.

Vinny P

[QUOTE=LV;3111704]I have a similar set up as well but new motors this winter , we do have 91, my builder said to splash 10-15 gallons of 110 in there just to make sure you are above /QUOTE]
My engine is brand new as well. Until now, I was able to safely run 89 in my previous engine. The fuel docks by me, have carried 91 for as long as I can remember. Now all of a sudden, I buld an engine that requires 91 and bang.... no more 91.

FuelinAround

Fuel distributors have to have a permit to be able to pump into a boat on water and around here it is a $50k slap on the wrist if you are filling anything other than a barge on water. As far as the ratios it really is as easy as percentages. If your local marine has switched to a 10% ethanol blend (which mercruiser states is safe for their marine motors) then your 89 is actually close to a 91 octane of they are splash blending. Anything over 10% has seemed to be a little to harsh for marine enviroments but most octane boosters are in fact ethanol or methanol based.

2Slow4me

Another thing to consider, apparently Ethenol has a lower BTU for the same otane.

In Canada, all stations buy shell have Ethenol.

Also the ethenol has caused some problems with many EFI engines here on the lake. (it cleans out everything inside)

Gasoline:
1 Gal Gasoline (mid grade) = 125,000 Btu's

Ethanol:
1 Gal Ethanol = 76,000 Btu's

1 Btu= .293 watt
1hp = 746 watts

Therefore, 101hp/ gallon of Ethanol, and 167 HP/gallon gas.

http://www.cogeneration.net/FuelAndE...quivalence.htm

FuelinAround

Correct....whenn your local fuel distributor switches to ethanol you need to change your fuel filters EXTREMELY reguarly for the first few fill ups. I changed mine every other weekend for 3 months when we switched. Rather be safe than sorry.

BY U BOY

I have heard that you can use toulene(sp) but never used it.

I always put some 110 in at the start of the season just in case. Running 10.7:1 i don't want to take any chances.

http://www.motorsportsracingfuels.co...alculator.html

FuelinAround

tolulene is a component of race gas so yes it helps raise octane. Lead is one of the larger factors in raising the octane of AV gas though.