[grandlake mariah z302]

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.

[mikeyt]

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

[WetWilly]

Hi grandlake mariah z302,

Looks like you've got a 125gal tank in your beast!

We use premium, either Shell or Chevron, it's because we have up to 10% ethanol so the quality isn’t that good. To get the best performance, and reduce any chance of getting engine ping we stay with the high test. Besides, with a 75 gal tank, the difference between Plus and Premium is only around $5 when it’s full. That’s not that much for a little peace of mind.

WetWilly

[grandlake mariah z302]

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".

[180diablo]

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 ...

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?

[ShabahZ280]

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.

[WetWilly]

Hi 180diablo,

See the new thread I posted in the Mercury MerCruiser section. Here

WetWilly

[mikeyt]

Originally Posted by 180diablo

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 ...
?

probably donkey pee....

[Z 202]

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.

[moondance100]

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