Octane question

[Daytomann]

Hey guys, got a quick octane question. I never thought about it untill this season when I noticed a tag on the Excalibur enginge cover.

I have been going off info from the PCM owners manual since day 1.

I've got an 04 216 TE with the 330hp Excalibur. The PCM owners manual says to run 87 octane, which I have done since the boat was new. But the spec tag on the back side of the red engine cover says to run 89.

I have not had any problems with the 87...so whats the deal? Should I switch to 89 or keep running 87?


Thanks!

[core-rider]

RE: Octane question

If you can run 87 and not hear any detonation (pre-ignition) then you will be fine. If you do hear pining, then go up in octane till it goes away.

I ran 89 in mine for a few years, but since prices went up I switched to 87. I haven't notice any problems so I am sticking with it.

[Daytomann]

RE: Octane question

No pinging at all so far.

[gride300]

RE: Octane question

i've run 87 in my 05 mc and 05 210. the mc reccomended 89 but i never noticed a difference. i use 87 now still

[TRDon]

RE: Octane question

I have a 93 pro boss with the converted ignition. I dont know if the timing is too agressive for use with 87 octane. Anyone else have a similar setup to mine and what do you run? The protec ignition called for 89 or better.

[DanielC]

RE: Octane question

Modern fuel injected engines have a knock sensor. The engines computer automattically retards the ignition timing if there is an engine knock, even before you are aware of the engines knock.
You can run 87 octane in an EFI engine designed to run 89 or higher octane.
An older engine than you set the ignition timing on, cannot compensate for the lower octane, you have to run the octane required, or retard the timing, or compensate in some other way.
If it is a cool humid day at a high altitude lake, the octane requirements are reduced. A warm dry day at sea level you will need higher octane.
Octane is a measurement of how fast the air fuel mixture burn in your engine. Higher octane, slower burn.
All other things being equal, and with no detonation, or knock, your engine will produce more power with lower octane.
That is right, in many cases the cheaper stuff will give you more power!
How you use your boat should also be taken into account when you decide what octane to use. If you use your boat for exclusively slalom skiing, or barefooting, I would use the recommended octane.
If you pull small childern on wakeboards with out ballast tanks filled, or swivel skiers, running the lower grade would probably be fine, especially in a modern EFI engine.

[AirTool]

Re: RE: Octane question

All other things being equal, and with no detonation, or knock, your engine will produce more power with lower octane.

Good point...however....the converse is true that having a higher octane fuel will allow for further advance of the timing which improves power.

AirTool

[DanielC]

RE: Re: RE: Octane question

If the engine is designed for 87 octane, running higher octane will not help. The computer has a preprogrammed amount of advance it will let the engine have. If you have an older engine that the timing is set manually, you could gain there. Most modern EFI engines will not let you set the timing.
Adjusting the timing for a different grade of gas is no longer "all things being equal"

[east tx skier]

RE: Re: RE: Octane question

I've been running 89 octane in my GT-40 since I came to own it last August. Last I checked, it costs about $3--$4 more per tank to run 89 assuming $.10--$.13 more per gallon.

[DanielC]

RE: Re: RE: Octane question

I also run 89 octane in my GT-40, but I have been to some lakes where my options are 87, and two stroke premix.

[AirTool]

RE: Re: RE: Octane question

We are planning a trip to Canyon Lake if a few weeks....called the marina yesterday to check of fuel costs.

89 octane is the only choice at 480 cents per gallon

[MHayes]

RE: Re: RE: Octane question

We have a GT40 in a 2001 Air and have always used 87 with no issues whatsoever. I just took another look at our manual and it states the following:

"Use any good grade of automotive regular or premium gasoline with a minimum average octane rating of 89. An 87 average octane gasoline may be used if 89 octane is not available."

[TwinTip]

This subject was brought up before and it seems that this was a typo on the stickers on the engine, they should have read 87. I have never checked on this but newer engines supposedly show 87 as the octane to be used. For more info please check the link below. Here one PN member that contacted PCM and was advised of the above.

http://www.planetnautique.com/index....opic&t=995