View Full Version : Engine selection/fuel availability

05-19-2020, 08:44 AM
I am considering engines for my project which will hopefully end up on floats. I wonder about trying to keep the compression low enough that auto fuel would be an option for use on lakes. What do you guys do when 100 might not be available. I was thinking that most marinas should be able to fuel me if I had a lower compression engine....
Is it worth the consideration for the loss of HP?



05-19-2020, 11:29 AM
Having an engine that can run mogas can save you the price of a rebuild over the life of the engine. Having fuel flexibility on long or remote trips is also very handy. When you want dependable power that lasts there is no replacement for displacement. Avoid high compression engines and fit the prop to the power/mission you have.

05-19-2020, 11:52 AM
Not familiar with marina gas, maybe Farmboy will chip in, but my concern would be ethanol mix.

All that said, I have had times where my choice was car gas, or walking. I fly a more remote part of the world than many, so your situation might be different.

For emergencies, you can carry octane boost to add to car gas and get the needed octane for a tank to get you to Aviation gas.

Where do you fly? That might make a difference.

Oh, a lower compression engine also is easier to hand prop out in the brush also.

05-20-2020, 05:41 AM
Displacement with 7.20:1 low compression, consider a Lycoming O-360-B1A, -B1B, -B2A, -B2B, -B2C. All are 168 hp and 80 Octane. All are stock unmodified engines.

Here's Lycoming's list: https://www.lycoming.com/sites/default/files/SSP-110-2%20Certified%20Engines.pdf

05-20-2020, 06:02 AM
Thank you! Those are the engines that I thought about using. IDK about "marina " gas either - as I am not a boater. I was just thinking what ever they sell would be be convenient to be able to run on. What to the guys do with the pumped up SuperCubs, etc? I suppose just do trips within their range....?

Thanks again,

05-20-2020, 07:24 AM
Another possibility, the engine in my Cub is an IO-360-B1D. The compression ratio is 8.50:1 and is rated at 180 hp. When you look at Lycoming's chart you will see several -Bxx rated at 180 hp. The chart says to use 100/100LL. The data tag on my engine is stamped 91 octane. It is likely that the chart doesn't mention 91 octane because it is no longer available.

My opinion is that any of those 8.50:1 engines would be safe to use 91 octane. In a pinch don't use full power, keep the throttle back a bit.

05-20-2020, 08:56 AM
If experimental, the titan O370 with 8.3:1 at 187 horse.

Sent from my iPad using SuperCub.Org

05-20-2020, 10:08 AM
.......IDK about "marina " gas either - as I am not a boater. I was just thinking what ever they sell would be be convenient to be able to run.....

Not sure, but I think the marina gas around here is ethanol-free.