What octane to run?

[kevnmcd]

I have read some stuff about this on some of the other sites but haven't seen anything on this here yet. Â*Since I will be taking delivery on my boat tomorrow (502 Mag MPI), what octane should I use? Â*I know that Mercury has said 87, but are there any advantages/disadvantages to running 89 or 91? Â*With my old motor (350), I always ran 91 in it cuz I had the timing set high to maximize the hp out of it. Â*With the new motor it is all electronic and set in the computer. Â*What are your thoughts....and, yes, let's even hear from you "performance boaters" Â*http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/wink.gif

[Red Horse]

Your ECM (Electronic Control Module) should control that for you. But some times that does not work. I always run some octane boost in my boat. Run at least the mid grade and go from there. And if it clatters, keep some octane boost in your boat to add. Berryman GO GO octane boost works really well for me.

[Essex502]

Kevin - I've burned everything from 87 to 91 - Pilot, Unocal, Shell, Terrible Herbst, Chevron, etc in our 502. What I can say is this....87 works just fine for everyday use. I do see some performance improvement when I drain the 87 and put fresh 91 Unocal in it. The ECM might be retarding the curve with the 87 but I can't know for sure. Mercruiser should know and they indeed recommend 87 in the manual. 91 won't do any harm but to your wallet and the boat definitely seems to be faster with it.

[kevnmcd]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Essex502 @ June 12 2003, 3:18 pm)</td></tr><tr><td id="QUOTE">.....and the boat definitely seems to be faster with it.[/QUOTE]<span id='postcolor'>
Well....that might be worth the extra $$$. http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[Trouble Maker]

No...it probably just seems faster because you spent more money....and you feel the internal need to justify the extra expense somehow...

Damn, I should be a shrink...

http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif Â*http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

Kevin...buy a little insurance just in case the lower grade isn't exactly 87 octane...use the mid-grade... You never know when your 87 Octane may only turn out to be 84.....you know what I mean??

[Essex502]

Extra speed seemed to be real...

The last weekend trip to Havasu before the BETA event we had less than 1/4 tank in both tanks. We made a run from the marina up to Topoc including a full speed pass. The best I could get on the GPS was 67 MPH. Now this gas had been in the tank since November. When we put the boat away for the winter we used Sta-Bil as always. Coming back from Topoc we "nursed" the boat to the Indian Casino as it was on empty on both tanks. I had never run it sooooo dry. Filled up both tanks (60 gallons total) with Unocal Premium. Left the Casino marina dock and drove down to Steamboat and BAMMM the boat was back up to 70 again on the GPS. Remember this is with 300# more weight (give or take a few) due to the full tanks. The two runs were within an hour of each other in the morning. Outside temp was around 75° or so. GPS used for both runs. At the BETA event we had the boat up to 70 again and were bumping the rev limiter somewhere around 5100 RPM at Lake Mojave which has to be a little higher elevation than Lake Havasu.

The facts...we have NEVER bumped the limiter with 87 octane regular. We routinely bump the limiter with 91 premium. Before this year the boat usually sat for a couple of months between trips so the gas may have gotten stale. We don't run flat out all the time so the test conditions are not always comparable.

All I know is I was quite suprised that the difference when we put the 91 in the tank this year after running the motor on 87 for the previous two years. I did break-in the motor as recommended with 91 for the first 20 or so hours.

Now...the variables...stale gas? Higher octane? Sta-bil? Time of day? direction of travel? wind? I don't know, it did certainly "act" different.

Just my impressions.....

[digginfordollars]

McD, if I had your kind of disposeable income, I run the high dollar stuff all the time. http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/rolleyes.gif

[TooMuchFun]

I've had similar experience as Essex502 ... whenever I'm about out of gas and have to fill up at Echo or Temple Bar and they are out of octane boost and I run 89 or 87 in my Volvo 600 (and my old 496) the difference was appreciable ... 4-5 mph and not the same acceleration.

Spend the extra money whenever you can ...

TooMuchFun

[kevnmcd]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (digginfordollars @ June 13 2003, 11:19 pm)</td></tr><tr><td id="QUOTE">McD, if I had your kind of disposeable income, I run the high dollar stuff all the time. http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/rolleyes.gif[/QUOTE]<span id='postcolor'>
http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/laugh.gif http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/laugh.gif http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/laugh.gif http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/laugh.gif

[Essex502]

60 gallons at an average delta of $0.20 per gallon = $12. Not gonna break the bank for any boater! http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[THOR]

100 octane kev. Nothing less. http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[kc0000]

That motor will consume anything you feed it, the ECU and the knock sensor will back off the timing to prevent any damage from poor fuel.

Same goes for oil, on a BB you need to check your oil EVERY time you take out the boat, with those hours it should consume a quart of oil every four to five hours. One quart down is 12%, two quarts down and you will notice a drop in performance due to heat in the motor and break down is vescocity.

[B-Rad502]

Kevin, I run 91 in my 502, but the computer has been recalibrated. It ran great on the 87 octane when it was stock. A buddy has a newer boat with a 500efi, he ran 91 for a while even though Mercruiser recommends only 87 for it. He ended up switching to 87 after a few months, now gets the same performance, A lOT less black transom, and much cheaper to fill up. Run a good quality 87 (Chevron or Texaco) and you'll be just fine. http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[Essex502]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (kc0000 @ June 16 2003, 9:08 pm)</td></tr><tr><td id="QUOTE">That motor will consume anything you feed it, the ECU and the knock sensor will back off the timing to prevent any damage from poor fuel.

Same goes for oil, on a BB you need to check your oil EVERY time you take out the boat, with those hours it should consume a quart of oil every four to five hours. Â*One quart down is 12%, two quarts down and you will notice a drop in performance due to heat in the motor and break down is vescocity.[/QUOTE]<span id='postcolor'>
KC - Interesting you should say that about oil...I've heard and read the same thing about the BBC's and I'm not seeing much oil consuption! I have only had to put 2 quarts in since I got the boat. That equates to only 75 hrs. or so but compared with what others are saying, seems I am rather lucky with this. <knock on wooden head> http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[Essex502]

Hey Thor...you have our boat in the background of your signature pic! Great!

[kevnmcd]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Essex502 @ June 17 2003, 07:11 am)</td></tr><tr><td id="QUOTE">Hey Thor...you have our boat in the background of your signature pic! Great![/QUOTE]<span id='postcolor'>
Mike - I noticed that, too. Was that taken at the RRX regatta last year?

[Essex502]

Must have been. Who's ass did Thor have to kiss to get the Logo'd signature? http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/confused.gif

[RUNNIN A FEVER]

Kev - I've also got the 502 MPI and was running 91. I had a very black transom. I thought it was the marina water but it was infact unburned fuel.

I don't belive the ECM will advance timming to get the best performance from 91, but will retard for poor quality gases.

Long story short I read in the Fountain forums that dyno, let me repeat that again, dyno testing showed that on our motors in stock form that HP was down 1-2 HP when using 91.

I personally run 89 and am very happy with the results.

[Essex502]

Interesting...we have never had the black transom disease with our 502. Runs very clean. It may be due to the fact that the exhaust at idle exits under the swim step and under water.

[kevnmcd]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Essex502 @ June 17 2003, 11:57 am)</td></tr><tr><td id="QUOTE">Who's ass did Thor have to kiss to get the Logo'd signature? http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif Â*http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/confused.gif[/QUOTE]<span id='postcolor'>
So....who's ass did you kiss? http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/laugh.gif

[kevnmcd]

Thanks for all the input, guys.

[OneBoatNut]

Will higher octane gasoline clean your engine better?
As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car’s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?
A few car engines may knock or ping — even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking
The Low Down on High Octane Gas.
Article courtesy of http://RacingSecrets.com

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner’s manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

What are octane ratings?
Octane ratings measure a gasoline’s ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.

What’s the right octane level for your car?
Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How can you tell if you’re using the right octane level?
Listen to your car’s engine. If it doesn’t knock when you use the recommended octane, you’re using the right grade of gasoline.

Will higher octane gasoline clean your engine better?
As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car’s engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?
A few car engines may knock or ping — even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is knocking harmful?
Occasional light knocking or pinging won’t harm your engine, and doesn’t indicate a need for higher octane. But don’t ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?
The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you’re buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular


But hey why do dragsters run high octane? http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/biggrin.gif

[Essex502]

After the last three tanks of Unocal Premium in LHC, I am continually banging the rev limiter where I couldn't with the regular grade. That's usually with full or nearly full tanks, my wife and I, and all the gear for a day at the lake. Also, it doesn't seem to matter if it's 100° or 120° outside.

[kevnmcd]

E502 - Do you find that your transom has more scum on it with premium than with regular gas?

[ex cracker]

On my old boat I found that the transom got less dirty or black running premium with octane booster. The octane booster also made a big difference versus not using it.

[MOWtown]

Kevin, was there more exhaust scum on your transom at/after Powell than usual? It seemed that I was running very rich with darker, smellier exhaust. I'm assuming it was the elevation and, as you and I discussed, we didn't change the jets.

[ex cracker]

On the new boat with the 496HO I have run 1 tank of 91 and one tank of 87 and I also noticed about a 4 MPH difference at Lake Mead on back to back days with almost identicle conditions. The back of the boat also seemed to be less dirty or black with the higher octane and also seemed to clean off easier with the higher octane.

[kevnmcd]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (MOWtown @ July 30 2003, 08:06 am)</td></tr><tr><td id="QUOTE">Kevin, was there more exhaust scum on your transom at/after Powell than usual? Â*It seemed that I was running very rich with darker, smellier exhaust. Â*I'm assuming it was the elevation and, as you and I discussed, we didn't change the jets.[/QUOTE]<span id='postcolor'>
I have only run 87 octane in my boat so far. Â*I was very surprised how LITTLE scum there was on my transom. Â*With my boat next to KC's...you could see how much more scum he had than I did. Â*Mine was very clean for a week on the water.

MOW - Mine is an EFI motor so mine will electronically adjust for elevation. Â*So I didn't see any more than usual on my transom. Â*IMHO...EFI is much better than carburated. Â* http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/smile.gif

[Essex502]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (kevnmcd @ July 30 2003, 07:45 am)</td></tr><tr><td id="QUOTE">E502 - Do you find that your transom has more scum on it with premium than with regular gas?[/QUOTE]<span id='postcolor'>
Never, ever have I had any residue on the transom. Maybe it's due to the fact that the exhaust exits under water at idle. At WOT the exhaust is above water but that wouldn't be when the mixture is richest.

[Essex502]

It seems that the 496's make more "black scum" on the transoms than the 502's did as everyone with a 496 seems to report it happening.

[titties and beer]

I WENT FROM 91 TO 87 NO MORE BLACK http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/smile.gif

[Essex502]

T&B - You have the 496...right?

[kevnmcd]

I think T&B has the HP500.

[Essex502]

It's a Nordic, right? If so...exhaust is above the waterline.

[titties and beer]

500 HP ,IT WILL BE OUT OF THE WATER ON THE WAY TO CATALINA http://www.lasvegashotboats.com/iB_html/non-cgi/emoticons/wow.gif