195 premium fuel

[Ben West]

195 SVHO owners...89 octane plus booster vs. 93 octane. Thoughts? Expeiences? Just had to buy some marina gas today and they didn't have 93.

 

[probee773]

I've been using 93 octane pump gas with 10% or less ethanol. I didn't see a mention about ethanol free fuel in the owner's manual, but it does mention high octane, and I really want to avoid detonation/ knocking. I also use Sta Bil 360 marine additive...

https://www.amazon.com/gp/aw/d/B001...ta-bil+360&dpPl=1&dpID=41j5fKdIweL&ref=plSrch

 

[Ben West]

I've been using 93 octane pump gas with 10% or less ethanol. I didn't see a mention about ethanol free fuel in the owner's manual, but it does mention high octane, and I really want to avoid detonation/ knocking. I also use Sta Bil 360 marine additive...

https://www.amazon.com/gp/aw/d/B001...ta-bil+360&dpPl=1&dpID=41j5fKdIweL&ref=plSrch

I try to avoid ethanol when possible and have always ( one month of owning the boat) used 93. The particular marina that I had to stop at today only offered 89. Just got me thinking about maybe keeping a bottle of additive or octane booster on the boat. Just pumped 10 gallons to get us through the afternoon.

 

[kyle]

Im curious about this too. I have also only owned the boat a month and put on 19 hours, all which were 93 octane. Our favorite lake only sells 89 octane so I have been filling up three, five gallon jugs to take with us but that is such a pain. I knew this going into the deal and am willing to live with it for the performance but it is kind of annoying

 

[Ben West]

Im curious about this too. I have also only owned the boat a month and put on 19 hours, all which were 93 octane. Our favorite lake only sells 89 octane so I have been filling up three, five gallon jugs to take with us but that is such a pain. I knew this going into the deal and am willing to live with it for the performance but it is kind of annoying

Kyle, I agree. I usually bring 15 extra gallons. Gotta be sneaky around here about filling on the water as well. Not that I enjoy paying marina prices for premium, but sometimes, like today you may be caught low on fuel and 5-6 miles from the ramp.

 

[Jetswu87]

The boat requires 91+, I'd be adding some additives if 89 was available.

https://www.amazon.com/Torco-Accele...501517093&sr=8-1&keywords=torco+fuel+additive

Torco is legit, I have a hard time believing any of the store bought stuff.

 

[swatski]

Most "octane boosters" are snake oil but Torco is legit - MMT doesn't really boost octanes but rather retards the ignition. Same difference - prevents detonation.
I would carry a 16oz can if you are boating in areas where premium may not be available. It colors the plugs weird - orange/rusty - but not causing any problems.

--

 

[Ben West]

Ordered. Thanks gentlemen!

 

[druppert]

Well this post has sparked (pun intended) my own curiosity. A really smart dude explained octane to me (not a really smart dude) in a very simple fashion. He explained that octane rating has nothing to do with "fuel quality" or "engine cleaning properties" and everything to do with combustibility. The higher an engine's compression ratio the more likely it is to ignite the fuel before its proper timing due to heat created during the compression process. Modern engines can adjust their timing to mitigate this improper ignition pattern (knock) but they do so at the cost of efficiency & performance.

That's all well & good but I looked up the SVHO engine compression ratio out of curiosity & I see that it's only 8.5:1??? I'm pretty sure my lawnmower has a higher CR than that and I'm not kidding. So what gives? @Ben West I'm not trying to hijack your thread but you pose an excellent question regarding the necessity of high octane fuel and the stats & recommendations from Yamaha seem to contradict one another. I have only ever used premium in mine but if the SVHO engine CR is really only 8.5:1 I'm now seriously questioning whether it's necessary.

 

[viper15]

That's all well & good but I looked up the SVHO engine compression ratio out of curiosity & I see that it's only 8.5:1??? .

On a boosted engine (turbo or supercharger) you have to lower the compression ratio once you hit a certain level of boost. Similar to my 2015 Yamaha Viper snowmobile. It is running a stock compression ratio engine with an aftermarket turbo running about 5 pounds of boost. If I wanted to go higher than that, I would need to add an intercooler and a thicker shim on the engine head to lower the compression ratio. Boosted engines run a much higher risk of predetonation (like your friend explained to you). So by design, they have to run a lower compression ratio than a naturally aspirated engine.

 

[Ben West]

@druppert, great points. Hijack away! Here is what happened when I ran 89 octane...nothing. The boat ran great, no knocking or pinging. No noticable loss in performance. Granted, I only ran 10 gallons. I will stick to 91 plus, but in a pinch, seems to do fine.

 

[druppert]

Good to know! I'm towing the boat up to our lake house in NC Friday and plan to run many tanks of gas through it over the subsequent 10 days. I'll make sure at least 1 tank is 89. I'll post results here!

 

[druppert]

On a boosted engine (turbo or supercharger) you have to lower the compression ratio once you hit a certain level of boost.

Interesting. Is that because the charge heats the air before the engine compresses it further?

 

[viper15]

Interesting. Is that because the charge heats the air before the engine compresses it further?

The heat certainly has an affect on it. When you pump warm air into an engine, you are getting less air into it than if it was a cold charge ... thus less fuel goes along with it ... and less hp. That's where the intercooler comes in.

But it all comes down to compression ratio. Let's say for sake of argument, you have a naturally aspirated engine running at a compression ratio of 10:1. That means you are taking a volume of air that is 10 units in size, and compressing it down to 1 unit. When you add boost (via a turbo or super charger), you are effectively increasing that ratio. By volume you may still be at 10:1, but before compressing that volume of air the turbo or super compresses even more. Therefore, if you don't lower the compression ratio, a boosted engine will effectively run at a higher compression ratio. A higher compression ratio means more chance for predetonation.

An engine can usually handle a certain amount of added boost before you have to lower the compression ratio of the engine and add an intercooler to cool the charge. Usually around 4-5psi. But in any case, a boosted engine will run on that ragged edge of safe compression ratio. Therefore, to avoid a predetonation, you run a higher octance fuel. Can you get away with lower? - Probably. But the risk for damage is higher. Some engines will detect predetonation early enough to compensate - such as retard timing, limit boost, etc.

To the OP ... I always run the recommended 91+ octance. Have seen too many boosted snowmobile engines have catastrophic damage from running 87 octane.

 

[druppert]

Your explanation makes perfect sense. Fascinating stuff. I've learned something new. Back to 93 for me. Lol

 

[Ben West]

Your explanation makes perfect sense. Fascinating stuff. I've learned something new. Back to 93 for me. Lol

Ditto! Don't need no catastrophic failure!

 

[Wingfamily]

I realize this thread is a few years old, and although there are other threads discussing octane, I'm not seeing one that touches on the use of octane booster in place of 92 octane. We will be mooring our boat this coming season, and the port does not have a high octane fuel option. Can an octane booster be used to supplement the 4 octane differential?

 

[marcham]

Yes. I normally fill at Costco but when I fill on the water in BC only methanol free 89 is available. I've seen no impact after using octane booster vs 91.

 

[Julian]

@druppert, great points. Hijack away! Here is what happened when I ran 89 octane...nothing. The boat ran great, no knocking or pinging. No noticable loss in performance. Granted, I only ran 10 gallons. I will stick to 91 plus, but in a pinch, seems to do fine.

If only added 10 gallons of 89 to the 10 gallons of remaining 93 octane gas in your boat, you were effectively running 91 octane...which is what the boat calls for....thus no loss of power.

Also, for those seeking non-ethanol gas....doesn't ethanol increase octane?

 

[Neutron]

If only added 10 gallons of 89 to the 10 gallons of remaining 93 octane gas in your boat, you were effectively running 91 octane...which is what the boat calls for....thus no loss of power.

Also, for those seeking non-ethanol gas....doesn't ethanol increase octane?

Ethanol can make it run leaner but shouldn't affect octane rating