Gas
 

What octane gas is everybody running? My 99 Z302 has a 502 mag in it and calls for Premium. With a 120 gallon tank, I’m not looking forward to filling up, especially on the lake. At least i think its 120 gallon, first summer with new boat.

I usually run Shell mid range or sometimes premium in mine. I do see a 'slight' performance improvement on premium gas....

Colol , thanks guys. I was pretty much thinking the same thing, not much more for an overall cost to go with high grade, and like you said, i like "peace of mind".

Since my boat (and myself) are known for bragging about how much fuel my boat DOESN'T use compared to all the other members with 4.3L's and above ...
Can you guess what kind of fuel goes in my boat ... :rolleyes:

I know with automotive engines, unless the vehicle states that premium fuel is to be used, you are just wasting your money. I believe my boat is recommended for 87 Octane anyways.




Direct copy from the GM SI (service information) webpage on Facts/Myths for Maximizing Fuel economy:


Use the Recommended Grade (Octane) Fuel

Purchasing higher than required octane fuel is a waste of money. Using higher octane fuels in a vehicle that only required regular unleaded fuel will neither increase performance nor improve gas mileage. In all cases refer to your owners manual and ONLY use the octane rated fuel recommended for your vehicle.


Important: In high performance GM vehicles that DO require Premium (91 octane or higher) fuel, you MUST use fuels of at least this octane. Use of lower octane fuel may result in reduced performance, knocking, and/or permanent engine damage not covered under the terms of the New Vehicle Warranty.


Now I know this is in relation to a vehicle, but I wondered how much of this would mirror on use in the boat motors?

Anyone care to try and elaborate on fuel octane use in motors for boats specifically?

Seems to me I read that Mercruiser recommends 87 Octane for their engines. Now for their "Mag" engines, i'm not sure. I run 87 when I'm able to fill up on land, and will buy 89 on the water, as it's the lowest octane available around here on the water.

probably donkey pee.... :rolling_laugh:

I put regular old 87 octane in mine, and fill it up at the gas station (vs the Marina) as often as possible. Gas is 15 cents/liter more expensive at the dock, which really adds up on a whole tank (150 liters). Thankfully my annual slip fee includes unlimited launch priviledges.

87 when all petroleum....89 with ethanol....

$3.37 a gal. for regular, and now you say I should move up a grade because of ethanol. It already takes $400.00 to fill up.

I'm sure that I am not the smartest person on this board. With that said...My understanding is that octane is the resistance for predetonation. The higher the compression of your engine the higher octane you need to prevent predetonation. If your engine does not need a high octane to prevent predetonation (87) and you put high octane in it, then you will see no advantage.

People sometime confuse high octane with high performance. If your engine is built with high compression then high octane is needed and you will see a loss when using low octane fuel (predetonation). If your engine is build for low octane (low compression) you will see no improvement when useing high octane.

There are several websites that discuss octane ratings if you need to find out what fuel to run to get the most out of your boat without wasting money.

Hi KSP181

I don’t think anyone here can claim their the smartest, that’s for sure… that said, you’re absolutely correct about the pre-detonation and if anyone is interested in learning more about Octane they can click here: octane rating.

There is one situation where higher octane can improve your performance - at times when the engine is under extreme loads such as a boat very heavily loaded with people and gear and expected to run flat out. The higher octane would suppress pre-ignition allowing a higher top speed because the operator would not have to back the RPMs off as soon due to engine pinging. This is the same for a tow vehicle when pulling a grade

There’s a little know secret - there are vehicles designed to run on 87 octane, but when higher octane is used, the computer recalibrates the fuel injector duty cycles and engine timing to take advantage of the higher octane (or lack of ping). One such example is the Ford Triton series. Though the gains are small (I have heard up to 6%), it can make a difference while towing and acceleration. I have tried it out myself after hearing of this back in 97 and later on our 99 with a re-programmer for the engine computer.

Hey Mariah Z276, if the octane you’re using does not ping when you’re out and about, then you’re OK, but if you’ve got the knock, it’s up the grade of gas or look at getting another motor some time in the near furture. What’s an extra $5 to $10 bucks compared to another motor, right?

Believe me when I say I totally sympathize with everyone with larger V8 motors. For the last 24 years, I ran a 3.0L and now I have a 7.4L. So you can imagine what I'm having to get used to at the gas pump. What makes it worse is, many stations here limit the dollar amount per fill up to $50.00. That won't even fill the Expedition's tank let alone put a dent in the Talari's...OUCH, but I figure that's the price I have to pay for that extra gettiyup and go! :(

Sorry, just my $0.02, make that $0.04 worth of ranting,
WetWilly

$3.37 for regular? What a bargain! Everyplace I'm seeing is $3.60-$3.65!!! I only burn about 5-10 gallons per week. If someone wants to ski or kneeboard, they better bring a $50 bill with them!

Thats good news. I don't have any pinging. It was mentioned earlier in the thread that with ethanol you need to up the octane. Thanks to you and KSP181 for the explanation.

Around here most gas stations dump all the ethanol in during the winter, which kills your winter mileage. So it's less likely to be an issue during the boating season.

As stated in the Mercruiser link WetWilly provided, the merc design should handle 87 octane with up to 10% ethanol, and as noted, the only reason to go higer is if you are experiencing detonation when under load.

There is a lot of good information about fuel in this thread! :wink_thumbup:

I think im going to give my 3.0 a hug when I get up to the cottage.
lol.

Uh, I think there may be a law against getting intimate with your sterndrive.... :eek_animated:

Ummm no .. only in Alabama there is :D

As I've said before the most important thing is to stay away from gas with Ethanol in it! At most marinas this won't be a problem but a lot of us fill up at gas stations before getting to the water. This is where you have to be careful. Most mix 10% ethanol with their gas now.

All summer last year I was using road gas vs marina gas. I would always be bringing gas cans down to the boat and filling it up at my uncles dock.

I burn 87 octane as suggested in the manual and never have problems. I never use gas with ethanol in my boat or auto.